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Document And Entity Information - shares	6 Months Ended
Document And Entity Information - shares	Jun. 30, 2018	Jul. 27, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	ICF International, Inc.
Entity Central Index Key	0001362004
Trading Symbol	ICFI
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		18,860,323
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands

Jun. 30, 2018

Dec. 31, 2017

Current Assets:

Cash and cash equivalents

$ 6,322

$ 11,809

Contract receivables, net

174,652

168,318

Contract assets

130,241

123,197

Prepaid expenses and other assets

16,393

11,327

Income tax receivable

12,134

5,596

Restricted cash - current

^[1]

11,191

Total Current Assets

339,742

331,438

Property and Equipment, net

44,937

38,052

Other Assets:

Goodwill

693,027

686,108

Other intangible assets, net

33,437

35,304

Restricted cash - non-current

1,279

1,266

Other assets

22,129

18,087

Total Assets

1,134,551

1,110,255

Current Liabilities:

Accounts payable

63,705

75,074

Contract liabilities

25,886

38,571

Accrued salaries and benefits

44,125

45,645

Accrued subcontractors and other direct costs

30,228

47,508

Accrued expenses and other current liabilities

24,891

17,572

Total Current Liabilities

188,835

224,370

Long-term Liabilities:

Long-term debt

243,645

206,250

Deferred rent

14,214

15,119

Deferred income taxes

34,831

33,351

Other

17,655

15,135

Total Liabilities

499,180

494,225

Commitments and Contingencies (Note 14)

Stockholders’ Equity:

Preferred stock, par value $.001; 5,000,000 shares authorized; none issued

Common stock, par value $.001; 70,000,000 shares authorized; 22,328,695 and 22,019,315 shares issued as of June 30, 2018 and December 31, 2017, respectively; 18,825,993 and 18,661,801 shares outstanding as of June 30, 2018 and December 31, 2017, respectively

Additional paid-in capital

317,013

307,821

Retained earnings

456,358

434,766

Treasury stock

(130,446)

(121,540)

Accumulated other comprehensive loss

(7,576)

(5,039)

Total Stockholders’ Equity

635,371

616,030

Total Liabilities and Stockholders’ Equity

$ 1,134,551

$ 1,110,255

[1]	Restricted cash – current as of December 31, 2017 represents amount held in an escrow account for the acquisition of The Future Customer. See Note 10 – Business Combination.

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	70,000,000	70,000,000
Common stock, issued (in shares)	22,328,695	22,019,315
Common stock, outstanding (in shares)	18,825,993	18,661,801

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue	$ 324,315	$ 306,392	$ 627,095	$ 602,687
Direct costs	206,565	190,896	395,391	374,503
Operating costs and expenses:
Indirect and selling expenses	90,410	86,240	180,069	175,042
Depreciation and amortization	4,045	4,299	8,514	8,818
Amortization of intangible assets	2,270	2,749	4,514	5,483
Total operating costs and expenses	96,725	93,288	193,097	189,343
Operating income	21,025	22,208	38,607	38,841
Interest expense	(2,167)	(2,537)	(3,833)	(4,488)
Other (expense) income	(318)	226	(214)	335
Income before income taxes	18,540	19,897	34,560	34,688
Provision for income taxes	4,923	7,960	8,526	12,574
Net income	$ 13,617	$ 11,937	$ 26,034	$ 22,114
Earnings per Share:
Basic	$ 0.72	$ 0.64	$ 1.39	$ 1.17
Diluted	$ 0.71	$ 0.63	$ 1.36	$ 1.15
Weighted-average Shares:
Basic	18,806	18,775	18,738	18,840
Diluted	19,209	19,086	19,208	19,252
Cash dividends declared per common share	$ 0.14		$ 0.28
Other comprehensive (loss) income, net of tax	$ (3,317)	$ 2,100	$ (1,708)	$ 2,472
Comprehensive income, net of tax	$ 10,300	$ 14,037	$ 24,326	$ 24,586

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities
Net income	$ 26,034	$ 22,114
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Non-cash equity compensation	5,347	5,361
Depreciation and amortization	13,027	14,301
Facilities consolidation reserve	(127)	1,625
Deferred taxes and other adjustments, net	1,339	4,421
Changes in operating assets and liabilities:
Net contract assets and liabilities	(19,658)	(13,813)
Contract receivables, net	(5,971)	6,952
Prepaid expenses and other assets	(7,115)	(2,978)
Accounts payable	(11,283)	(9,953)
Accrued salaries and benefits	(1,378)	(3,375)
Accrued subcontractors and other direct costs	(17,280)	(6,550)
Accrued expenses and other current liabilities	3,757	(2,326)
Income tax receivable and payable	(7,315)	(5,441)
Other liabilities	(1,102)	6,307
Net Cash (Used in) Provided by Operating Activities	(21,725)	16,645
Cash Flows from Investing Activities
Capital expenditures for property and equipment and capitalized software	(9,397)	(6,083)
Payments for business acquisitions, net of cash received	(11,838)	(91)
Net Cash Used in Investing Activities	(21,235)	(6,174)
Cash Flows from Financing Activities
Advances from working capital facilities	284,773	348,975
Payments on working capital facilities	(247,378)	(330,363)
Payments on capital expenditure obligations	(3,131)	(2,276)
Debt issue costs	(21)	(1,489)
Proceeds from exercise of options	3,533	2,431
Dividends Paid	(2,635)
Net payments for stockholder issuances and buybacks	(8,597)	(25,253)
Net Cash Provided by (Used in) Financing Activities	26,544	(7,975)
Effect of Exchange Rate Changes on Cash, Cash Equivalents, and Restricted Cash	(249)	366
(Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash	(16,665)	2,862
Cash, Cash Equivalents, and Restricted Cash, Beginning of Period	24,266	7,885
Cash, Cash Equivalents, and Restricted Cash, End of Period	7,601	10,747
Supplemental Disclosure of Cash Flow Information
Interest	3,641	3,923
Income taxes	11,490	$ 12,982
Non-cash investing and financing transactions:
Capital expenditure obligations	$ 6,121

Basis of Presentation and Nature of Operations

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Basis of Presentation and Nature of Operations

NOTE 1 - BASIS OF PRESENTATION AND NATURE OF OPERATIONS

Basis of Presentation

The accompanying consolidated financial statements include the accounts of ICF International, Inc. and its subsidiaries (collectively, the “Company”), and have been prepared in accordance with United States (“U.S.”) generally accepted accounting principles (“U.S. GAAP”). All significant intercompany transactions and balances have been eliminated.

Nature of Operations

The Company provides professional services and technology-based solutions to government and commercial clients, including management, marketing, technology, and policy consulting and implementation services in the areas of: energy, environment, and infrastructure; health, education and social programs; safety and security; and consumer and financial services. The Company offers a full range of services to these clients throughout the entire life cycle of a policy, program, project, or initiative, from research, analysis, assessment and advice to design and implementation of programs and technology-based solutions, as well as the provision of engagement services and programs.

The Company’s major clients are U.S. federal government departments and agencies, most significantly the Department of Health and Human Services, Department of State and Department of Defense. The Company also serves U.S. state and local government departments and agencies, international governments, and commercial clients worldwide. Commercial clients include airlines, airports, electric and gas utilities, oil companies, banks and other financial services companies, transportation, travel and hospitality firms, non-profits/associations, law firms, manufacturing firms, retail chains, and distribution companies. The term “federal” or “federal government” refers to the U.S. federal government, and “state and local” or “state and local government” refers to U.S. state and local governments, unless otherwise indicated.

The Company, incorporated in Delaware, is headquartered in Fairfax, Virginia. It maintains offices throughout the world, including over 55 offices in the U.S. and U.S. territories and more than 15 offices in key regions outside the U.S., including offices in the United Kingdom, Belgium, China, India, and Canada.

Interim Results

The unaudited consolidated financial statements included in this Quarterly Report on Form 10-Q have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). These rules and regulations permit some of the information and footnote disclosures normally included in financial statements, prepared in accordance U.S. GAAP, to be condensed or omitted. In management’s opinion, the unaudited consolidated financial statements contain all adjustments that are of a normal recurring nature, necessary for a fair presentation of the results of operations and financial position of the Company for the interim periods presented. The Company reports operating results and financial data in one operating and reportable segment. Operating results for the three-months and six-months period ended June 30, 2018 are not necessarily indicative of the results that may be expected for the full year. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2017 and the notes thereto included in the Company’s Annual Report on Form 10-K, filed with the SEC on February 28, 2018 (the “Annual Report”).

Reclassifications

Certain amounts in the 2017 consolidated financial statements have been reclassified to conform to the current year presentation. As a result of the adoption of Accounting Standard Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606), the Company presented balances entitled contract assets and contract liabilities within the consolidated balance sheet as well as the impact of changes in these balances within the consolidated statement of cash flows. The Company reclassified comparable balances within the December 31, 2017 consolidated balance sheet as well as the impact of changes in these balances within the consolidated statement of cash flows in order to enhance comparability. Any other reclassifications were immaterial to the financial statements taken as a whole.

Significant Accounting Policies

Revenue Recognition

The Company primarily provides services and technology-based solutions to clients that operate in a variety of markets and may span the entire program life cycle, from initial research and analysis to the design and implementation of solutions. The Company enters into agreements with clients that create enforceable rights and obligations and for which it is probable that the Company will collect the consideration to which it will be entitled as services and solutions are transferred to the client. Except in certain narrowly defined situations, the Company’s agreements with its clients are written and revenue is generally not recognized on oral or implied arrangements. The Company recognizes revenue based on the consideration specified in the agreement and excludes from revenue amounts collected on behalf of third parties. Accordingly, sales and similar taxes which are collected for third parties are excluded from the transaction price. The Company also evaluates whether two or more agreements should be accounted for as one single contract and whether combined or single agreements should be accounted for as more than one performance obligation.

For most contracts, the client requires the Company to perform a number of tasks in providing an integrated output and, hence, each of these contracts are tracked as having only one performance obligation. When contracts are separated into multiple performance obligations, the Company allocates the total transaction price to each performance obligation based on the estimated relative standalone selling prices of the promised services underlying each performance obligation. The Company generally provides customized solutions in which the pricing is based on specific negotiations with each client, and, in these cases, the Company uses a cost plus margin approach to estimate the standalone selling price of each performance obligation. It is common for the Company’s long-term contracts to contain award fees, incentive fees or other provisions that can either increase or decrease the transaction price. These variable amounts are generally awarded at the completion of a prescribed measurement period based on the achievement of performance metrics, program milestones or cost targets, and the amount awarded may be subject to client discretion. The Company estimates variable consideration as the most likely amount to which the Company expects to be entitled.

Long-term contracts typically contain billing terms that provide for invoicing once a month and payment on a net 30-day basis. Exceptions to monthly billing terms are to ensure that the Company performs satisfactorily rather than representing a significant financing component. For cost-based contracts, the Company’s performance is evaluated during a contractually stipulated performance period and, while contract costs may be billed on a monthly basis, the Company is generally permitted to bill for incentive or award fees only after the completion of the performance period, which may occur quarterly, semi-annually or annually, and after the client completes the performance assessment. Fixed-price contracts may provide for milestone billings based on the attainment of specific project objectives rather than for billing on a monthly basis. Moreover, contracts may require retentions or hold backs that are paid at the end of the contract to ensure that the Company performs in accordance with requirements. The Company does not assess whether a contract contains a significant financing component if the Company expects, at contract inception, that the period between payment by the client and the transfer of promised services to the client will be one year or less.

The Company generally recognizes revenue over time as control is transferred to a client, based on the extent of progress towards satisfaction of the performance obligation. The selection of the method used to measure progress requires judgment and is dependent on the contract type selected by the client during contract negotiation and the nature of the services and solutions to be provided.

When a performance obligation is billed using a time-and-materials contract type, the Company uses output progress measures to estimate revenue earned based on hours worked in contract performance at negotiated billing rates. Fixed-price level-of-effort contracts are substantially similar to time-and-materials contracts except that the Company is required to deliver a specified level of effort over a stated period of time. For these contracts, the Company estimates revenue earned using contract hours worked at negotiated bill rates as the Company delivers the contractually required workforce.

For cost-based contracts, the Company recognizes revenue based on contract costs incurred, as the Company becomes contractually entitled to reimbursement of the contract costs, plus a most likely estimate of award or incentive fees earned on those costs even though final determination of fees earned occurs after the contractually-stipulated performance assessment period ends.

For performance obligations requiring the delivery of a service for a fixed price, the Company uses the ratio of actual costs incurred to total estimated costs, provided that costs incurred (an input method) provides a reasonable measure of progress towards the satisfaction of a performance obligation, in order to estimate the portion of total revenue earned. When this method is used, changes in estimated costs to complete these obligations result in adjustments to revenue on a cumulative catch-up basis, which causes the effect of revised estimates for prior periods to be recognized in the current period. Changes in these estimates can routinely occur over contract performance for a variety of reasons, which include: changes in contract scope; changes in contract cost estimates due to unanticipated cost growth or reassessments of risks impacting costs; changes in estimated incentive or award fees; or performing better or worse than previously estimated.

In some fixed price service contracts, the Company performs services of a recurring nature, such as maintenance and other services of a “stand ready” nature. For these contracts, the Company has the right to consideration in an amount that corresponds directly with the value that the client has received. Therefore, the Company records revenue on a straight-line basis to reflect the transfer of control to the client throughout the contract.

Contracts are often modified to reflect changes in contract specifications and requirements, and these changes may create new enforceable rights and obligations. Most modifications are for services that are not distinct from the existing agreement due to the significant integration service that the Company provides. Therefore, most modifications are accounted for as part of an existing performance obligation. The effect of these modifications on transaction price, and the Company’s measure of progress in fulfilling the performance obligation to which it relates, may be recognized as an adjustment to revenue on a cumulative catch-up basis. Revenue from modifications that create new, distinct performance obligations is recognized based on the Company’s progress in fulfilling the requirements of the new obligation.

For contracts in which the estimated cost to perform exceeds the consideration to be received, the Company accrues for the entire estimated loss during the period in which the loss is determined by recording additional direct costs.

The Company recognizes the cost to fulfill contracts as incurred. The Company evaluates incremental costs of obtaining a contract and, if they are recoverable from the client and relate to a specific future contract, they are deferred and recognized over contract performance or the estimated life of the customer relationship if renewals are expected. The Company expenses these costs when incurred if the amortization period is one year or less.

Unfulfilled performance obligations represent amounts expected to be earned on contracts and do not include the value of negotiated, unexercised contract options, which are classified as marketing offers. Indefinite delivery/indefinite quantity and similar arrangements provide a framework for the client to issue specific tasks, delivery or purchase orders in the future and these arrangements are considered marketing offers until a specific order is executed.

Revenue recognition entails the use of significant judgment, including, but not limited to, the following: evaluating agreements in terms of the number and nature of performance obligations, determining the appropriate method for measuring progress to satisfaction of obligations, and preparing estimates in terms of the amount of progress that the Company has made. Most of the Company’s revenue is recognized over time and for many fixed-price contracts, in particular, the Company estimates the proportion of total revenue earned using the ratio of contract costs incurred to total estimated contract costs, which requires the Company to prepare estimates as work progresses of contract cost left to be incurred. Moreover, some of the Company’s contracts include variable consideration, which requires the Company to estimate the most likely amounts that will be earned over the respective performance periods. For these obligations, changes in estimates result in cumulative catch-up adjustments and may have a significant impact on earnings during a given period.

The Company’s operating cycle for long-term contracts may be greater than one year and is measured by the average time intervening between the inception and the completion of those contracts. Contract-related assets and liabilities, as highlighted below, are classified as current assets and current liabilities. Significant balance sheet accounts related to the revenue recognition cycle are as follows:

Contract receivables, net – This account includes amounts billed or billable under contract terms. The amounts due are stated at their net realizable value. The Company maintains an allowance for doubtful accounts to provide for the estimated amount of receivables that will not be collected. The Company considers a number of factors in its estimate of the allowance, including knowledge of a client’s financial condition, its historical collection experience, and other factors relevant to assessing the collectability of the receivables.

Contract assets – This account includes unbilled amounts typically resulting from revenue recognized on long-term contracts when the amount of revenue recognized exceeds the amounts billed. It also includes contract retainages until the Company has met the contract-stipulated requirements for payment. Contract assets are reported in a net position on a contract by contract basis each period even though individual contracts may contain multiple performance obligations. On a contract by contract basis, amounts do not exceed their net realizable value.

Contract liabilities – This account consists of advance payments received and billings in excess of revenue recognized on long-term contracts. Contact liabilities are reported in a net position on a contract by contract basis each period even though individual contracts may contain multiple performance obligations.

Recent Accounting Pronouncements

Recent Accounting Pronouncements Adopted

Accumulated Other Comprehensive Loss

In February 2018, the Financial Accounting Standards Board (“FASB”) issued ASU 2018-02: Income Statement – Reporting Comprehensive Income (Topic 220). Certain transactions were recorded in accumulated other comprehensive income in the past, net of tax. The tax had been calculated based on the tax rates enacted at the time the transaction occurred with no provision, under previous accounting, for adjusting the balance for changes in the enacted tax rate. Due to the passage of the Tax Cuts and Jobs Act of 2017 (the “Tax Act”), those historical rates were higher than the Company’s current tax rate. The new guidance allows the Company to reclassify these stranded tax effects directly to retained earnings. This update is effective for fiscal years beginning after December 15, 2018, including interim periods therein, and early adoption is permitted. During the first quarter of 2018, the Company elected to early adopt the update, which resulted in a one-time cumulative effect adjustment of $0.8 million from accumulated other comprehensive loss to retained earnings.

Revenue Recognition

The Company implemented ASU 2014-09, Revenue from Contracts with Customers (Topic 606), on January 1, 2018 using the modified retrospective method. This method requires that the Company apply the requirements of the new standard in the year of adoption to new contracts and those that were not completed as of the adoption date. Management evaluated those contracts not completed as of January 1, 2018 (or adoption date) and concluded that the impact of adopting ASC 606 did not have a material impact on the Company. Contract assets and contract liabilities were formerly reported as unbilled accounts receivable and deferred revenue, respectively. The titles have been changed in the table below to be consistent with accounts currently used under the new standard.

	December 31, 2017
	As Reported		As Adopted
Contract receivables, net	$	291,515	$	168,318
Contract assets		—		123,197
Deferred revenue		38,571		—
Contract liabilities		—		38,571
Retained earnings		434,766		434,766

Unfulfilled performance obligations for contracts in process as of the adoption date were $1.1 billion.

Under the modified retrospective method, the Company is required to maintain dual reporting during the year of adoption in order to present revenue under both the previous and new accounting for contracts initiated on or after the date of adoption and for those contracts having remaining obligations as of the adoption date. Revenue timing differences between the two methods resulted primarily from contracts with performance incentives. Under the new accounting, the Company has included in revenue the most likely amount of priced incentives earned as contract work was performed rather than, as under the old accounting, waiting to recognize revenue from incentives until specific quantitative goals were achieved, generally at the end of the measurement period. This timing difference is not expected to result in a material change to the Company’s annual revenue since most incentives have a one-year measurement period, which is aligned with the Company’s fiscal year. Revenue calculated under the old and new methods is as follows:

	Three months ended June 30, 2018				Six months ended June 30, 2018
	Previous Accounting		New Accounting		Previous Accounting		New Accounting
Revenue	$	323,559	$	324,315	$	625,795	$	627,095

Contract assets		129,298		130,241		129,298		130,241
Contract liabilities		26,243		25,886		26,243		25,886

Recent Accounting Pronouncements Not Yet Adopted

Leases

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This standard revises the accounting for leases and requires lessees to recognize, for all leases with terms of greater than one year, a right-of-use asset and lease liability which depicts the rights and obligations arising from a lease. The standard also requires qualitative and quantitative disclosures designed to provide information regarding the nature, amount and timing of lease expense. For lessees, the new guidance is not expected to significantly change the recognition and measurement of lease expense. This update is effective for the first interim and annual periods beginning after December 15, 2018, with early adoption permitted. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842), Targeted Improvements permitting the recognition of a cumulative-effect adjustment to retained earnings on the date of adoption. The Company currently intends to adopt the standard on January 1, 2019, utilizing the alternative transition method. The Company is currently evaluating its leases, and designing new processes and controls that will aid in the implementation of and accounting for the new requirements. Until the implementation is completed, the Company cannot fully determine the effect of adopting the standard on the consolidated financial statements. However, the Company currently anticipates that, on adoption, the Company will recognize right-of-use assets and lease liabilities that will each total from $100 to $200 million. The Company does not expect a material impact on the results of operations and cash flows.

Stock Compensation

In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718). The standard simplifies the accounting for share-based compensation to non-employees by aligning the guidance with share-based payments to employees. It is effective for annual reporting periods beginning after December 15, 2018, and interim periods within those years, with early adoption permitted. The Company is currently in the process of evaluating the impact of adoption, but does not anticipate a material impact on the consolidated financial statements.

Contract Receivables, Net

6 Months Ended

Jun. 30, 2018

Receivables [Abstract]

Contract Receivables, Net

NOTE 2 – CONTRACT RECEIVABLES, NET

Contract receivables, net consisted of the following:

	June 30, 2018			December 31, 2017
Billed and billable	$	178,115		$	172,171
Allowance for doubtful accounts		(3,463	)		(3,853	)
Contract receivables, net	$	174,652		$	168,318

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Goodwill

6 Months Ended

Jun. 30, 2018

Goodwill And Intangible Assets Disclosure [Abstract]

Goodwill

NOTE 3 – GOODWILL

The changes in the carrying amount of goodwill during the six-months period ended June 30, 2018 were as follows:

Balance as of December 31, 2017	$	686,108
Goodwill resulting from The Future Customer business combination		7,205
Effect of foreign currency translation		(286	)
Balance as of June 30, 2018	$	693,027

Long-Term Debt	6 Months Ended
Long-Term Debt	Jun. 30, 2018
Debt Disclosure [Abstract]
Long-Term Debt	NOTE 4 – LONG-TERM DEBT On May 17, 2017, the Company entered into a Fifth Amended and Restated Business Loan and Security Agreement with a syndication of 11 commercial banks (the “Credit Facility”). The Credit Facility: (i) includes modifications to the Company’s Fourth Amended and Restated Business Loan and Security Agreement, (ii) matures on May 17, 2022, (iii) increases the borrowing ceiling up to $600.0 million without a borrowing base requirement, taking into account financial, performance-based limitations, and (iv) provides for an “accordion,” which permits additional revolving credit commitments of up to $300.0 million, subject to lenders’ approval. The Credit Facility provides for letters of credit aggregating up to $60.0 million, which reduce the funds available under the Credit Facility when issued. The Company has the option to borrow funds under the Credit Facility at interest rates based on both LIBOR (1, 3, or 6 month rates) and the Base Rate, at its discretion, plus their applicable margins. Base Rates are fluctuating per annum rates of interest equal to the highest of (i) the Federal Funds Open Rate, plus 0.5%, (ii) the Prime Rate, and (iii) the daily LIBOR rate, plus a LIBOR Margin between 1.00% and 2.00% based on its Leverage Ratio (as defined under the Credit Facility). The interest accrued based on LIBOR rates is to be paid on the last business day of the interest period (1, 3, or 6 months), while interest accrued based on the Base Rates is to be paid in quarterly installments. The unused portion of the Credit Facility is subject to a commitment fee between 0.13% and 0.25% per annum based on the Leverage Ratio. The Credit Facility is collateralized by substantially all of the assets of the Company and requires that the Company remain in compliance with certain financial and non-financial covenants. The financial covenants require, among other things, that the Company maintain at all times an Interest Coverage Ratio (as defined under the Credit Facility) of not less than 3.00 to 1.00 and a Leverage Ratio of not more than 3.75 to 1.00 (subject to adjustment, in certain circumstances) for each fiscal quarter. As of June 30, 2018, the Company was in compliance with its covenants under the Credit Facility. As of June 30, 2018, the Company had $243.6 million long-term debt outstanding, 10 outstanding letters of credit totaling $3.2 million, and unused borrowing capacity of $353.2 million under the Credit Facility (excluding the accordion). Taking into account the financial, performance-based limitations, available borrowing capacity (excluding the accordion) was $200.3 million as of June 30, 2018. The weighted-average interest rate on debt outstanding was 3.0% and 2.6% for the first six months of 2018 and 2017, respectively.

Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss

6 Months Ended

Jun. 30, 2018

Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]

Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss

NOTE 5 – OTHER COMPREHENSIVE INCOME (LOSS) AND ACCUMULATED OTHER COMPREHENSIVE LOSS

Other comprehensive income (loss) includes foreign currency translation adjustments arising from the conversion of financial statements of foreign subsidiaries into U.S. dollars, the amortization of the gain on the sale of an interest rate hedge agreement, and the change in the fair value of a current interest rate hedge agreement. Components of accumulated other comprehensive loss as of June 30, 2018 and December 31, 2017 are as follows:

	Three Months Ended June 30, 2018
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾			Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at March 31, 2018	$	(7,708	)	$	2,563		$	886	$	(4,259	)
Current period other comprehensive income (loss):
Other comprehensive (loss) income before reclassifications		(3,366	)		—			181		(3,185	)
Amounts reclassified from accumulated other comprehensive income		—			(132	)		—		(132	)
Total current period other comprehensive (loss) income⁽⁴⁾		(3,366	)		(132	)		181		(3,317	)
Accumulated other comprehensive (loss) income at June 30, 2018	$	(11,074	)	$	2,431		$	1,067	$	(7,576	)

	Three Months Ended June 30, 2017
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾		Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at March 31, 2017	$	(11,443	)	$	2,175	$	—	$	(9,268	)
Current period other comprehensive income (loss):
Other comprehensive income before reclassifications ⁽⁴⁾		2,100			—		—		2,100
Accumulated other comprehensive (loss) income at June 30, 2017	$	(9,343	)	$	2,175	$	—	$	(7,168	)

	Six Months Ended June 30, 2018
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾			Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at December 31, 2017	$	(7,638	)	$	2,158		$	441	$	(5,039	)
Reclassification of stranded tax effects due to adoption of accounting principle⁽³⁾		(1,307	)		478			—		(829	)
Adjusted beginning balance		(8,945	)		2,636			441		(5,868	)
Current period other comprehensive (loss) income:
Other comprehensive (loss) income before reclassifications		(2,129	)		—			626		(1,503	)
Amounts reclassified from accumulated other comprehensive income		—			(205	)		—		(205	)
Total current period other comprehensive (loss) income⁽⁴⁾		(2,129	)		(205	)		626		(1,708	)
Accumulated other comprehensive (loss) income at June 30, 2018	$	(11,074	)	$	2,431		$	1,067	$	(7,576	)

	Six Months Ended June 30, 2017
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾		Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at December 31, 2016	$	(11,815	)	$	2,175	$	—	$	(9,640	)
Current period other comprehensive income (loss):
Other comprehensive income before reclassifications ⁽⁴⁾		2,472			—		—		2,472
Accumulated other comprehensive (loss) income at June 30, 2017	$	(9,343	)	$	2,175	$	—	$	(7,168	)

(1) - Represents the fair value of an interest rate hedge agreement, designated as a cash flow hedge, which was sold on December 1, 2016. The fair value of the interest rate hedge agreement was recorded in other comprehensive income, net of tax, and will be reclassified to earnings when earnings are impacted by the hedged items and as interest payments are made on the Credit Facility from January 31, 2018 to January 31, 2023.

(2) - Represents the change in fair value of an interest rate hedge agreement designated as a cash flow hedge, and entered into on August 31, 2017. The fair value of the interest rate hedge agreement was recorded in other comprehensive income and will be reclassified to earnings when earnings are impacted by the hedged items and as interest payments are made on the Credit Facility from August 31, 2018 to August 31, 2023.

(3) - The Company has adjusted the balance at December 31, 2017 of accumulated other comprehensive loss for the stranded tax effects caused by the enactment of the Tax Act.

(4) - Changes in other comprehensive income (loss) are shown net of a total tax benefit of $0.2 million and tax expense of $0.5 million for the three-months ended June 30, 2018 and 2017, respectively, and total tax expense of $0.1 million and $0.7 million for the six-months ended June 30,2018 and 2017, respectively.

Restricted Cash

6 Months Ended

Jun. 30, 2018

Cash And Cash Equivalents [Abstract]

Restricted Cash

NOTE 6 – RESTRICTED CASH

The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the consolidated balance sheet for the periods presented to the total of cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows for the six months ended June 30, 2018 and 2017:

	2018				2017
	Beginning		Ending		Beginning		Ending
Cash and cash equivalents	$	11,809	$	6,322	$	6,042	$	9,493
Restricted cash - current (1)		11,191		—		—		—
Restricted cash - non-current		1,266		1,279		1,843		1,254
Total of cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows	$	24,266	$	7,601	$	7,885	$	10,747

(1) - Restricted cash – current as of December 31, 2017 represents amount held in an escrow account for the acquisition of The Future Customer. See Note 10 – Business Combination.

Revenue Recognition

6 Months Ended

Jun. 30, 2018

Disaggregation Of Revenue [Abstract]

Revenue Recognition

NOTE 7 – REVENUE RECOGNITION

Disaggregation of Revenue

The Company disaggregates revenue from clients, most of which is earned over time, into categories that depict how the nature, amount and uncertainty of revenue and cash flows are affected by economic factors. Those categories are: client market, client type and contract mix. Client market provides insight into the breadth of the Company’s expertise. In classifying revenue by client market, the Company attributes revenue from a client to the market that the Company believes is the client’s primary market. The Company also classifies revenue by the type of entity for which it does business, which is an indicator of the diversity of its client base. The Company attributes revenue generated as a subcontractor to a commercial company as government revenue when the ultimate client is a government agency or department. Finally, disaggregation by contract mix provides insight in terms of the degree of performance risk that the Company has assumed. Fixed-price contracts are considered to provide the highest amount of performance risk as the Company is required to deliver a scope of work or level of effort for a negotiated fixed price. Time-and-materials contracts require the Company to provide skilled employees on contracts for negotiated fixed hourly rates. Since the Company is not required to deliver a scope of work, but merely skilled employees, it considers these contracts to be less risky than a fixed-price agreement. Cost-based contracts are considered to provide the lowest amount of performance risk since the Company is generally reimbursed for all contract costs incurred in performance of contract deliverables with only the amount of incentive or award fees (if applicable) dependent on the achievement of negotiated performance requirements.

	June 30, 2018
	Three Months Ended		Six Months Ended
Client Markets:
Energy, environment, and infrastructure	$	132,563	$	256,318
Health, education, and social programs		131,624		255,189
Safety and security		27,491		52,927
Consumer and financial		32,637		62,661
Total	$	324,315	$	627,095

	June 30, 2018
	Three Months Ended		Six Months Ended
Client Type:
U.S. federal government	$	138,875	$	272,597
U.S. state and local government		35,267		67,172
International government		34,508		63,245
Total Government		208,650		403,014
Commercial		115,665		224,081
Total	$	324,315	$	627,095

	June 30, 2018
	Three Months Ended		Six Months Ended
Contract Mix:
Fixed-price	$	136,178	$	258,825
Time-and-materials		128,243		252,268
Cost-based		59,894		116,002
Total	$	324,315	$	627,095

Contract Balances:

Contract assets consist primarily of unbilled amounts resulting from long-term contracts when revenue recognized exceeds the amount billed due to billing schedule timing. Contract liabilities result from advance payments received on a contract or from billings in excess of revenue recognized on long-term contracts due to billing schedule timing. The $19.7 million increase in the Company’s net contract assets (liabilities) is due to the timing of work performed in relation to billing schedule timing for fixed price programs, particularly in our international operations. There were no material changes to contract balances due to impairments or business combinations during the period.

	June 30, 2018			At date of adoption			Change
Contract asset	$	130,241		$	123,197		$	7,044
Contract liabilities		(25,886	)		(38,571	)		12,685
Net contract assets (liabilities)	$	104,355		$	84,626		$	19,729

Performance Obligations:

The Company had $1.2 billion in unfulfilled performance obligations as of June 30, 2018, which primarily entail the future delivery of services for which revenue will be recognized over time. The obligations relate to continued or additional services required on contracts and were generally valued using an estimated cost plus margin approach, with variable consideration being estimated at the most likely amount. The Company expects to satisfy these performance obligations, on average, in one year.

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 8 – INCOME TAXES The Company’s effective tax rate for the three and six months ended June 30, 2018 and 2017 was 26.6% and 40.0% and 24.7% and 36.3%, respectively. The Company is subject to federal income taxes in the U.S. as well as to taxes in various state, local and foreign jurisdictions. Tax statutes and regulations within each jurisdiction are subject to interpretation and require the application of significant judgment. The Company’s 2014 through 2016 tax years remain subject to examination by the Internal Revenue Service for federal tax purposes. Certain significant state, local and foreign tax returns also remain open under the applicable statute of limitations and are subject to examination for the tax years from 2013 to 2016. The Company’s total liability for unrecognized tax benefits as of June 30, 2018 was $1.1 million. Included in the balance as of June 30, 2018 was $1.0 million in tax positions that, if recognized, would have a favorable impact on the Company’s effective tax rate. The Company believes it is reasonably possible that, during the next 12 months, the Company’s liability for uncertain tax benefits may decrease by approximately $0.7 million. The Company’s policy is not to recognize accrued interest and penalties related to unrecognized tax benefits as a component of tax expense. The Company has made no provision for deferred U.S. income taxes or additional foreign taxes on future unremitted earnings of its controlled foreign subsidiaries because the Company considers these earnings to be permanently invested. On December 20, 2017, the U.S. Congress passed the Tax Act, which was signed into law on December 22, 2017 and is generally effective beginning January 1, 2018. The Company will be impacted in several ways as a result of the Tax Act, including, but not limited to, provisions which include a permanent reduction in the U.S. federal corporate income tax rate from 35% to 21%. The Company has not completed the accounting for the tax effects of the enactment of the Tax Act; however, in certain cases, as described below, the Company made a provisional estimate of the effects on existing deferred tax balances and the one-time transition tax in the period of enactment. The Company recognized the provisional estimate as a reduction in the provision for income taxes during the fourth quarter of 2017. The Company re-measured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. However, the Company is still analyzing certain aspects of the Tax Act and refining estimates, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts. Pursuant to U.S. Securities and Exchange Commission Staff Accounting Bulletin 118 (“SAB 118”), the provisional amount recorded related to the re-measurement of the deferred tax balances has not been adjusted during the six months ended June 30, 2018. The one-time “transition tax” is based on the Company’s total post-1986 earnings and profits (“E&P”) which the Company has previously deferred from U.S. income taxation. The Company has not yet completed the calculation of the total post-1986 foreign E&P and related foreign tax pools for these foreign subsidiaries. Further, the transition tax is based in part on the amount of those earnings held in cash and other specified assets. This amount, as well as the related foreign tax credit utilization, may change when the Company finalizes the calculation of post-1986 foreign E&P and related foreign tax pools that were previously deferred from U.S. federal taxation and once the Company finalizes the amounts held in cash or other specified assets. Similarly, the cumulative foreign tax credit carry forward balance as of December 31, 2017 and any valuation allowance required (as applicable) may also change. No additional income taxes have been provided for on any remaining undistributed foreign earnings not subject to the transition tax and any additional outside basis difference inherent in these foreign entities because these amounts continue to be permanently reinvested in foreign operations. Pursuant to SAB 118, the provisional amount recorded related to the transition tax has not been adjusted during the six months ended June 30, 2018. The impact of the re-measurement of the deferred tax balances and the transition tax are preliminary estimates and will not be finalized until the latter part of 2018. The Tax Act subjects U.S. corporations to current tax on global intangible low-taxed income (or “GILTI”) earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740 No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI resulting from those items in the year the tax is incurred. The Company elected in the first quarter of fiscal year 2018 to recognize the resulting tax on GILTI as a period expense in the period the tax is incurred. The current provision for 2018 included no tax expense for GILTI.

Accounting for Stock Compensation	6 Months Ended
Accounting for Stock Compensation	Jun. 30, 2018
Accounting For Stock Based Compensation [Abstract]
Accounting for Stock Compensation	NOTE 9 – ACCOUNTING FOR STOCK COMPENSATION On April 4, 2018, the Company’s board of directors approved the 2018 Omnibus Incentive Plan (the “2018 Omnibus Plan”), which was subsequently approved by the stockholders and became effective on May 31, 2018 (the “Effective Date”). The 2018 Omnibus Plan replaced the previous 2010 Omnibus Incentive Plan (the “Prior Plan”). On or after the Effective Date, the 2018 Omnibus Plan allows the Company to grant 1,185,000 shares of stock options, stock appreciation rights, restricted stock, restricted stock units (“RSUs”), performance units and performance share awards (“PSAs”), cash-based awards, and other stock-based awards to all officers, key employees, and non-employee directors of the Company. Outstanding shares granted under the Prior Plan, totaling 608,154 as of June 30, 2018, will remain subject to its terms and conditions, and no additional awards from the Prior Plan are to be made after the Effective Date. As of June 30, 2018, the Company had approximately 1,185,000 shares available for grant under the 2018 Omnibus Plan. Cash-settled RSUs (“CSRSUs”) have no impact on the shares available for grant under the Omnibus Plan, nor on the calculated shares used in earnings per share (“EPS”) calculations. During the six months ended June 30, 2018, the Company granted to its employees 159,749 shares in the form of RSUs with an average grant date fair value of $61.62, and the equivalent value of 145,980 shares in the form of CSRSUs with an average grant date fair value of $60.74. During the six months ended June 30, 2018, the Company also granted 45,136 shares in the form of PSAs to its employees with a grant date fair value of $66.68 per share. The RSUs, CSRSUs and PSAs granted are generally subject to service-based vesting conditions, with the PSAs also having performance-based vesting conditions. The performance conditions for the PSAs granted in 2018 have a performance period from January 1, 2018 through December 31, 2020 and the performance conditions are consistent with the PSAs granted in 2017. The Company’s performance-based share program is further described in “Note 13—Accounting for Stock-Based Compensation,” in the “Notes to Consolidated Financial Statements” in the Annual Report. The Company recognized stock-based compensation expense of $5.4 million and $4.7 million for the three months ended June 30, 2018 and 2017, respectively, and $10.2 million and $8.2 million for the six months ended June 30, 2018 and 2017, respectively. Unrecognized compensation expense of approximately $14.9 million as of June 30, 2018 related to unsettled RSUs is expected to be recognized over a weighted-average period of 2.0 years. The unrecognized compensation expense related to CSRSUs totaled approximately $22.0 million at June 30, 2018 and is expected to be recognized over a weighted-average period of 2.0 years. Unrecognized compensation expense related to PSAs of approximately $4.7 million as of June 30, 2018 is expected to be recognized over a weighted-average period of 1.4 years.

Business Combination	6 Months Ended
Business Combination	Jun. 30, 2018
Business Combinations [Abstract]
Business Combination	NOTE 10 – BUSINESS COMBINATION In January 2018, the Company acquired The Future Customer (“TFC”), a leading boutique loyalty strategy and marketing company based in London (U.K.) The acquisition of TFC enhanced and extended the Company’s customer loyalty business to Europe. The acquisition was not significant to the Company’s financial statements taken as a whole.

Earnings Per Share

6 Months Ended

Jun. 30, 2018

Earnings Per Share [Abstract]

Earnings Per Share

NOTE 11 – EARNINGS PER SHARE

EPS is computed by dividing reported net income by the weighted-average number of shares outstanding. Diluted EPS considers the potential dilution that could occur if common stock equivalents were exercised or converted into stock. The difference between the basic and diluted weighted-average equivalent shares with respect to the Company’s EPS calculation is due entirely to the assumed exercise of stock options and the vesting and settlement of RSUs and PSAs. PSAs are included in the computation of diluted shares only to the extent that the underlying performance conditions (i) are satisfied as of the end of the reporting period or (ii) would be considered satisfied if the end of the reporting period were also the end of the applicable performance period and the result would be dilutive under the treasury stock method.

As of June 30, 2018, the PSAs granted during the year ended December 31, 2016 met the related performance conditions for the initial performance period and were included in the calculation of diluted EPS. However, the PSAs granted during the year ended December 31, 2017 and during the six months ended June 30, 2018 have not yet completed their initial two-year performance period and therefore were excluded in the calculation of diluted EPS. There were no weighted-average shares excluded from the calculation of EPS because they were anti-dilutive for the three months ended June 30, 2018 and 2017, respectively, as well as for the six months ended June 30, 2017. There were 12,415 shares excluded for the six months ended June 30, 2018. The anti-dilutive shares were associated with RSUs.

The dilutive effect of stock options, RSUs, and PSAs for each period reported is summarized below:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017		2018		2017
Net Income	$	13,617	$	11,937	$	26,034	$	22,114

Weighted-average number of basic shares outstanding during the period		18,806		18,775		18,738		18,840
Dilutive effect of stock options, RSUs, and performance shares		403		311		470		412
Weighted-average number of diluted shares outstanding during the period		19,209		19,086		19,208		19,252

Basic earnings per share	$	0.72	$	0.64	$	1.39	$	1.17
Diluted earnings per share	$	0.71	$	0.63	$	1.36	$	1.15

Share Repurchase Program	6 Months Ended
Share Repurchase Program	Jun. 30, 2018
Equity [Abstract]
Share Repurchase Program	NOTE 12 – SHARE REPURCHASE PROGRAM The Company’s current share repurchase program allows for share repurchases in the aggregate up to $100.0 million under share repurchase plans approved by the board of directors pursuant to Rules 10b5-1 and 10b-18 under the Securities Exchange Act of 1934. As part of the Company’s modification of the Credit Facility, the Credit Facility limits on share repurchases were eliminated to permit unlimited share repurchases, provided the Company’s Leverage Ratio, prior to and after giving effect to such repurchases, is not greater than 3.25 to 1.00. As of June 30, 2018, $95.0 million remained available for share repurchases. Share repurchases also include shares surrendered by employees to satisfy tax withholding obligations in connection with the issuance of restricted stock, RSUs and PSAs.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	NOTE 13 – SUBSEQUENT EVENTS On August 2, 2018, the Company’s board of directors approved a $0.14 per share cash dividend. The dividend will be paid on October 16, 2018 to shareholders as of the close of business on September 7, 2018.

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 14 – COMMITMENTS AND CONTINGENCIES Litigation and Claims The Company is involved in various legal matters and proceedings arising in the ordinary course of business. While these matters and proceedings cause it to incur costs, including, but not limited to, attorneys’ fees, the Company currently believes that any ultimate liability arising out of these matters and proceedings will not have a material adverse effect on its financial position, results of operations, or cash flows. Road Home Contract On June 10, 2016, the Office of Community Development (the “OCD”) of the State of Louisiana filed a written administrative demand with the Louisiana Commissioner of Administration against ICF Emergency Management Services, L.L.C. (“ICF Emergency”), a subsidiary of the Company, in connection with ICF Emergency’s administration of the Road Home Program (“Program”). The Program contract was a three-year, $912 million contract awarded to the Company in 2006. The Program ended, as scheduled, in 2009. The Program was primarily intended to help homeowners and landlords of small rental properties affected by Hurricanes Rita and Katrina. In its administrative demand, the OCD sought approximately $200.8 million in alleged overpayments to the Program’s grant recipients. The State of Louisiana separately supplemented the amount of recovery it is seeking in total to approximately $220.2 million. The State of Louisiana, through the Division of Administration, also filed suit in Louisiana state court on June 10, 2016. The State of Louisiana broadly alleges and seeks recoupment for the same claim made in the administrative proceeding submission before the Louisiana Commissioner of Administration. On September 21, 2016, the Commissioner of the Division of Administration notified OCD and the Company of his decision to defer jurisdiction of the administrative demand filed by the OCD. In so doing, the Commissioner declined to reach a decision on the merits and stated that his deferral would not be deemed to grant or deny any portion of the OCD’s claim. The Commissioner subsequently authorized the parties to proceed on the matter in the previously filed judicial proceeding. The Company continues to believe that this claim has no merit and intends to vigorously defend its position. The Company has therefore not recorded a liability.

Basis of Presentation and Nature of Operations (Policies)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Basis of Presentation

Revenue Recognition

Recent Accounting Pronouncements

Recent Accounting Pronouncements Adopted

Accumulated Other Comprehensive Loss

Revenue Recognition

	December 31, 2017
	As Reported		As Adopted
Contract receivables, net	$	291,515	$	168,318
Contract assets		—		123,197
Deferred revenue		38,571		—
Contract liabilities		—		38,571
Retained earnings		434,766		434,766

Unfulfilled performance obligations for contracts in process as of the adoption date were $1.1 billion.

	Three months ended June 30, 2018				Six months ended June 30, 2018
	Previous Accounting		New Accounting		Previous Accounting		New Accounting
Revenue	$	323,559	$	324,315	$	625,795	$	627,095

Contract assets		129,298		130,241		129,298		130,241
Contract liabilities		26,243		25,886		26,243		25,886

Recent Accounting Pronouncements Not Yet Adopted

Leases

Stock Compensation

Basis of Presentation and Nature of Operations (Tables)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Schedule of Contract Assets, Contract Liabilities and Calculation of Revenue under Old and New Accounting Pronouncements

	December 31, 2017
	As Reported		As Adopted
Contract receivables, net	$	291,515	$	168,318
Contract assets		—		123,197
Deferred revenue		38,571		—
Contract liabilities		—		38,571
Retained earnings		434,766		434,766

Unfulfilled performance obligations for contracts in process as of the adoption date were $1.1 billion.

	Three months ended June 30, 2018				Six months ended June 30, 2018
	Previous Accounting		New Accounting		Previous Accounting		New Accounting
Revenue	$	323,559	$	324,315	$	625,795	$	627,095

Contract assets		129,298		130,241		129,298		130,241
Contract liabilities		26,243		25,886		26,243		25,886

Contract Receivables, Net (Tables)

6 Months Ended

Jun. 30, 2018

Receivables [Abstract]

Summary of Contract Receivables, Net

Contract receivables, net consisted of the following:

	June 30, 2018			December 31, 2017
Billed and billable	$	178,115		$	172,171
Allowance for doubtful accounts		(3,463	)		(3,853	)
Contract receivables, net	$	174,652		$	168,318

Goodwill (Tables)

6 Months Ended

Jun. 30, 2018

Goodwill And Intangible Assets Disclosure [Abstract]

Schedule of Changes in Carrying Amount of Goodwill

The changes in the carrying amount of goodwill during the six-months period ended June 30, 2018 were as follows:

Balance as of December 31, 2017	$	686,108
Goodwill resulting from The Future Customer business combination		7,205
Effect of foreign currency translation		(286	)
Balance as of June 30, 2018	$	693,027

Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss (Tables)

6 Months Ended

Jun. 30, 2018

Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]

Components of Other Comprehensive Income and Components of Accumulated Other Comprehensive Loss

	Three Months Ended June 30, 2018
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾			Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at March 31, 2018	$	(7,708	)	$	2,563		$	886	$	(4,259	)
Current period other comprehensive income (loss):
Other comprehensive (loss) income before reclassifications		(3,366	)		—			181		(3,185	)
Amounts reclassified from accumulated other comprehensive income		—			(132	)		—		(132	)
Total current period other comprehensive (loss) income⁽⁴⁾		(3,366	)		(132	)		181		(3,317	)
Accumulated other comprehensive (loss) income at June 30, 2018	$	(11,074	)	$	2,431		$	1,067	$	(7,576	)

	Three Months Ended June 30, 2017
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾		Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at March 31, 2017	$	(11,443	)	$	2,175	$	—	$	(9,268	)
Current period other comprehensive income (loss):
Other comprehensive income before reclassifications ⁽⁴⁾		2,100			—		—		2,100
Accumulated other comprehensive (loss) income at June 30, 2017	$	(9,343	)	$	2,175	$	—	$	(7,168	)

	Six Months Ended June 30, 2018
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾			Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at December 31, 2017	$	(7,638	)	$	2,158		$	441	$	(5,039	)
Reclassification of stranded tax effects due to adoption of accounting principle⁽³⁾		(1,307	)		478			—		(829	)
Adjusted beginning balance		(8,945	)		2,636			441		(5,868	)
Current period other comprehensive (loss) income:
Other comprehensive (loss) income before reclassifications		(2,129	)		—			626		(1,503	)
Amounts reclassified from accumulated other comprehensive income		—			(205	)		—		(205	)
Total current period other comprehensive (loss) income⁽⁴⁾		(2,129	)		(205	)		626		(1,708	)
Accumulated other comprehensive (loss) income at June 30, 2018	$	(11,074	)	$	2,431		$	1,067	$	(7,576	)

	Six Months Ended June 30, 2017
	Foreign Currency Translation Adjustments			Gain on Sale of Interest Rate Hedge Agreement ⁽¹⁾		Change in Fair Value of Interest Rate Hedge Agreement ⁽²⁾		Total
Accumulated other comprehensive (loss) income at December 31, 2016	$	(11,815	)	$	2,175	$	—	$	(9,640	)
Current period other comprehensive income (loss):
Other comprehensive income before reclassifications ⁽⁴⁾		2,472			—		—		2,472
Accumulated other comprehensive (loss) income at June 30, 2017	$	(9,343	)	$	2,175	$	—	$	(7,168	)

(3) - The Company has adjusted the balance at December 31, 2017 of accumulated other comprehensive loss for the stranded tax effects caused by the enactment of the Tax Act.

Restricted Cash (Tables)

6 Months Ended

Jun. 30, 2018

Restricted Cash And Cash Equivalents Current [Abstract]

Reconciliation of Cash and Cash Equivalents, and Restricted Cash

	2018				2017
	Beginning		Ending		Beginning		Ending
Cash and cash equivalents	$	11,809	$	6,322	$	6,042	$	9,493
Restricted cash - current (1)		11,191		—		—		—
Restricted cash - non-current		1,266		1,279		1,843		1,254
Total of cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows	$	24,266	$	7,601	$	7,885	$	10,747

(1) - Restricted cash – current as of December 31, 2017 represents amount held in an escrow account for the acquisition of The Future Customer. See Note 10 – Business Combination.

Revenue Recognition (Tables)

6 Months Ended

Jun. 30, 2018

Disaggregation Of Revenue [Abstract]

Disaggregation of Revenue

	June 30, 2018
	Three Months Ended		Six Months Ended
Client Markets:
Energy, environment, and infrastructure	$	132,563	$	256,318
Health, education, and social programs		131,624		255,189
Safety and security		27,491		52,927
Consumer and financial		32,637		62,661
Total	$	324,315	$	627,095

	June 30, 2018
	Three Months Ended		Six Months Ended
Client Type:
U.S. federal government	$	138,875	$	272,597
U.S. state and local government		35,267		67,172
International government		34,508		63,245
Total Government		208,650		403,014
Commercial		115,665		224,081
Total	$	324,315	$	627,095

	June 30, 2018
	Three Months Ended		Six Months Ended
Contract Mix:
Fixed-price	$	136,178	$	258,825
Time-and-materials		128,243		252,268
Cost-based		59,894		116,002
Total	$	324,315	$	627,095

Schedule of Contract Balances and Changes in Contract Balances

Contract Balances:

	June 30, 2018			At date of adoption			Change
Contract asset	$	130,241		$	123,197		$	7,044
Contract liabilities		(25,886	)		(38,571	)		12,685
Net contract assets (liabilities)	$	104,355		$	84,626		$	19,729

Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2018

Earnings Per Share [Abstract]

Schedule of Dilutive Effect of Stock Options RSUs and PSAs

The dilutive effect of stock options, RSUs, and PSAs for each period reported is summarized below:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017		2018		2017
Net Income	$	13,617	$	11,937	$	26,034	$	22,114

Weighted-average number of basic shares outstanding during the period		18,806		18,775		18,738		18,840
Dilutive effect of stock options, RSUs, and performance shares		403		311		470		412
Weighted-average number of diluted shares outstanding during the period		19,209		19,086		19,208		19,252

Basic earnings per share	$	0.72	$	0.64	$	1.39	$	1.17
Diluted earnings per share	$	0.71	$	0.63	$	1.36	$	1.15

Basis of Presentation and Nature of Operations - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) Office Segment	Jan. 01, 2018 USD ($)
Basis of Presentation and Nature of Operations [Line Items]
Number of operating segments \| Segment	1
Number of reportable segments \| Segment	1
Contract payment term description	Contracts typically contain billing terms that provide for invoicing once a month and payment on a net 30-day basis.
Contracts receivable, term	1 month
Contracts payment, term	30 days
Unfulfilled performance obligation	$ 1,200.0	$ 1,100.0
New Accounting Pronouncement Early Adoption Effect \| ASU 2018-02
Basis of Presentation and Nature of Operations [Line Items]
Reclassification of tax effects from accumulated other comprehensive loss to retained earnings	0.8
Minimum \| ASU 2016-02
Basis of Presentation and Nature of Operations [Line Items]
Right-of-use assets and lease liabilities	100.0
Maximum \| ASU 2016-02
Basis of Presentation and Nature of Operations [Line Items]
Right-of-use assets and lease liabilities	$ 200.0
Domestic \| Minimum
Basis of Presentation and Nature of Operations [Line Items]
Number of offices \| Office	55
International \| Minimum
Basis of Presentation and Nature of Operations [Line Items]
Number of offices \| Office	15

Basis of Presentation and Nature of Operations - Schedule of Contract Assets and Contract Liabilities Reported under New Accounting Standard (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Contract receivables, net	$ 174,652	$ 168,318
Contract assets	130,241	123,197
Contract liabilities	25,886	38,571
Retained earnings	456,358	434,766
ASU 2014-09 \| As Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Contract receivables, net		291,515
Contract assets	129,298	123,197
Deferred revenue		38,571
Contract liabilities	$ 26,243	38,571
Retained earnings		$ 434,766

Basis of Presentation and Nature of Operations - Schedule of Revnue Claculated under Old and New Accounting Methods (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue	$ 324,315	$ 627,095
Contract assets	130,241	130,241	$ 123,197
Contract liabilities	25,886	25,886	38,571
ASU 2014-09 \| As Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue	323,559	625,795
Contract assets	129,298	129,298	123,197
Contract liabilities	$ 26,243	$ 26,243	$ 38,571

Contract Receivables, Net - Summary of Contract Receivables, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Billed and billable	$ 178,115	$ 172,171
Allowance for doubtful accounts	(3,463)	(3,853)
Contract receivables, net	$ 174,652	$ 168,318

Goodwill - Schedule of Changes in Carrying Amount of Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Balance as of December 31, 2017	$ 686,108
Goodwill resulting from business combinations	7,205
Effect of foreign currency translation	(286)
Balance as of June 30, 2018	$ 693,027

Long-Term Debt - Additional Information (Details)		6 Months Ended
Long-Term Debt - Additional Information (Details)	May 17, 2017 USD ($) Bank	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017
Debt Instrument [Line Items]
Credit facility syndication, number of commercial banks \| Bank	11
Line of credit facility, expiration date		May 17, 2022
Line of credit facility, maximum borrowing capacity without borrowing base requirement	$ 600,000,000
Line of credit facility, accordion feature, additional revolving credit commitments under existing loan facility	300,000,000
Line of credit facility, maximum borrowing capacity	$ 60,000,000
Line of credit facility, interest coverage ratio covenant	300.00%
Line of credit facility, leverage ratio covenant	375.00%
Long-term debt		$ 243,645,000	$ 206,250,000
Number of letters of credit, outstanding		10
Letters of credit outstanding, amount		$ 3,200,000
Line of credit facility, remaining borrowing capacity		353,200,000
Line of credit facility, current borrowing capacity		$ 200,300,000
Long-term debt, weighted average interest rate, at point in time		3.00%		2.60%
Minimum
Debt Instrument [Line Items]
Line of Credit Facility, Committement Fee Unused Capacity	0.13%
Maximum
Debt Instrument [Line Items]
Line of Credit Facility, Committement Fee Unused Capacity	0.25%
Federal Funds Open Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.50%
London Interbank Offered Rate (LIBOR) \| Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.00%
London Interbank Offered Rate (LIBOR) \| Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%

Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss - Components of Other Comprehensive Income and Components of Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2018

Jun. 30, 2017

Jun. 30, 2018

Jun. 30, 2017

Accumulated Other Comprehensive Income Loss [Line Items]

Accumulated other comprehensive (loss) income

$ 616,030

Current period other comprehensive income (loss):

Total current period other comprehensive (loss) income

$ (3,317)

$ 2,100

(1,708)

$ 2,472

Accumulated other comprehensive (loss) income

635,371

Foreign Currency Translation Adjustments

Accumulated Other Comprehensive Income Loss [Line Items]

Accumulated other comprehensive (loss) income

(7,708)

(11,443)

(7,638)

(11,815)

Reclassification of stranded tax effects due to adoption of accounting principle

^[1]

(1,307)

Adjusted beginning balance

(8,945)

Current period other comprehensive income (loss):

Other comprehensive (loss) income before reclassifications

(3,366)

2,100

^[2]

(2,129)

2,472

Total current period other comprehensive (loss) income

(3,366)

^[2]

(2,129)

Accumulated other comprehensive (loss) income

(11,074)

(9,343)

(11,074)

(9,343)

Gain on Sale of Interest Rate Hedge Agreement

Accumulated Other Comprehensive Income Loss [Line Items]

Accumulated other comprehensive (loss) income

^[3]

2,563

2,175

2,158

2,175

Reclassification of stranded tax effects due to adoption of accounting principle

^[1],[3]

478

Adjusted beginning balance

^[3]

2,636

Current period other comprehensive income (loss):

Amounts reclassified from accumulated other comprehensive income

^[3]

(132)

(205)

Total current period other comprehensive (loss) income

^[3]

(132)

^[2]

(205)

Accumulated other comprehensive (loss) income

^[3]

2,431

2,175

2,431

2,175

Change in Fair Value of Interest Rate Hedge Agreement

Accumulated Other Comprehensive Income Loss [Line Items]

Accumulated other comprehensive (loss) income

^[4]

886

441

Adjusted beginning balance

^[4]

441

Current period other comprehensive income (loss):

Other comprehensive (loss) income before reclassifications

^[4]

181

626

Total current period other comprehensive (loss) income

^[4]

181

^[2]

626

Accumulated other comprehensive (loss) income

^[4]

1,067

Accumulated Other Comprehensive Loss

Accumulated Other Comprehensive Income Loss [Line Items]

Accumulated other comprehensive (loss) income

(4,259)

(9,268)

(5,039)

(9,640)

Reclassification of stranded tax effects due to adoption of accounting principle

^[1]

(829)

Adjusted beginning balance

(5,868)

Current period other comprehensive income (loss):

Other comprehensive (loss) income before reclassifications

(3,185)

2,100

^[2]

(1,503)

2,472

Amounts reclassified from accumulated other comprehensive income

(132)

(205)

Total current period other comprehensive (loss) income

(3,317)

^[2]

(1,708)

Accumulated other comprehensive (loss) income

$ (7,576)

$ (7,168)

$ (7,576)

$ (7,168)

[1]	The Company has adjusted the balance at December 31, 2017 of accumulated other comprehensive loss for the stranded tax effects caused by the enactment of the Tax Act.
[2]	Changes in other comprehensive income (loss) are shown net of a total tax benefit of $0.2 million and tax expense of $0.5 million for the three-months ended June 30, 2018 and 2017, respectively, and total tax expense of $0.1 million and $0.7 million for the six-months ended June 30,2018 and 2017, respectively
[3]	Represents the fair value of an interest rate hedge agreement, designated as a cash flow hedge, which was sold on December 1, 2016. The fair value of the interest rate hedge agreement was recorded in other comprehensive income, net of tax, and will be reclassified to earnings when earnings are impacted by the hedged items and as interest payments are made on the Credit Facility from January 31, 2018 to January 31, 2023.
[4]	Represents the change in fair value of an interest rate hedge agreement designated as a cash flow hedge, and entered into on August 31, 2017. The fair value of the interest rate hedge agreement was recorded in other comprehensive income and will be reclassified to earnings when earnings are impacted by the hedged items and as interest payments are made on the Credit Facility from August 31, 2018 to August 31, 2023.

Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss - Components of Other Comprehensive Income and Components of Accumulated Other Comprehensive Loss (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Other comprehensive income (loss), net of total tax (benefit) expense	$ (0.2)	$ 0.5	$ 0.1	$ 0.7

Restricted Cash - Reconciliation of Cash and Cash Equivalents, and Restricted Cash to the Total of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($)
$ in Thousands

Jun. 30, 2018

Dec. 31, 2017

Jun. 30, 2017

Dec. 31, 2016

Cash And Cash Equivalents [Abstract]

Cash and cash equivalents

$ 6,322

$ 11,809

$ 9,493

$ 6,042

Restricted cash - current

^[1]

11,191

Restricted cash - non-current

1,279

1,266

1,254

1,843

Total of cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows

$ 7,601

$ 24,266

$ 10,747

$ 7,885

[1]	Restricted cash – current as of December 31, 2017 represents amount held in an escrow account for the acquisition of The Future Customer. See Note 10 – Business Combination.

Revenue Recognition - Disaggregation of Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Revenue from clients	$ 324,315	$ 306,392	$ 627,095	$ 602,687
Fixed-Price [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	136,178		258,825
Time-and-Materials [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	128,243		252,268
Cost-Based [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	59,894		116,002
U S Federal Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	138,875		272,597
U.S. State and Local Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	35,267		67,172
International Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	34,508		63,245
Total Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	208,650		403,014
Commercial
Disaggregation Of Revenue [Line Items]
Revenue from clients	115,665		224,081
Energy, Environmental and Infrastructure [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	132,563		256,318
Health, Education and Social Programs [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	131,624		255,189
Safety and Security [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	27,491		52,927
Consumer and Financial [Member]
Disaggregation Of Revenue [Line Items]
Revenue from clients	$ 32,637		$ 62,661

Revenue Recognition - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018
Disaggregation Of Revenue [Line Items]
Net contract assets (liabilities)	$ 104,355
Unfulfilled performance obligation	$ 1,200,000	$ 1,100,000
Expected period to satisfy performance obligations	1 year
ASU 2014-09 \| Increase in Net Contract Assets (Liabilities)
Disaggregation Of Revenue [Line Items]
Net contract assets (liabilities)	$ 19,729

Revenue Recognition - Schedule of Changes in Contract Balances Due to Adoption of New Accounting Standards (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Revenue From Contract With Customer Balances Of Net Contract Assets Liabilities [Line Items]
Contract asset	$ 130,241	$ 123,197
Contract liabilities	(25,886)	(38,571)
Net contract assets (liabilities)	104,355
ASU 2014-09 \| As Reported
Revenue From Contract With Customer Balances Of Net Contract Assets Liabilities [Line Items]
Contract asset	129,298	123,197
Contract liabilities	(26,243)	(38,571)
Net contract assets (liabilities)		$ 84,626
ASU 2014-09 \| Change
Revenue From Contract With Customer Balances Of Net Contract Assets Liabilities [Line Items]
Contract asset	7,044
Contract liabilities	12,685
Net contract assets (liabilities)	$ 19,729

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Taxes [Line Items]
Effective income tax rate reconciliation, percent	26.60%	40.00%	24.70%	36.30%
Unrecognized tax benefits	$ 1,100,000		$ 1,100,000
Unrecognized tax benefits that would impact effective tax rate	1,000,000		1,000,000
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	700,000		700,000
Additional income taxes for remaining undistributed foreign earnings not subject to transition tax	$ 0		0
Global Intangible Low-Tax Income
Income Taxes [Line Items]
Current provision for global intangible low-tax income			$ 0
Internal Revenue Service (IRS) \| Earliest Tax Year
Income Taxes [Line Items]
Open tax year			2014
Internal Revenue Service (IRS) \| Latest Tax Year
Income Taxes [Line Items]
Open tax year			2016
State Local and Foreign Jurisdictions \| Earliest Tax Year
Income Taxes [Line Items]
Open tax year			2013
State Local and Foreign Jurisdictions \| Latest Tax Year
Income Taxes [Line Items]
Open tax year			2016

Accounting for Stock Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Apr. 04, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated share-based compensation expense		$ 5.4	$ 4.7	$ 10.2	$ 8.2
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				159,749
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 61.62
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		14.9		$ 14.9
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				2 years
Cash Settled RSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				145,980
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 60.74
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		22.0		$ 22.0
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				2 years
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				45,136
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value				$ 66.68
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized		$ 4.7		$ 4.7
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition				1 year 4 months 24 days
Omnibus Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares grants	1,185,000			608,154
Share-based compensation arrangement by share-based payment award, number of shares available for grant		1,185,000		1,185,000
Share-based compensation arrangement by share-based payment award, number of additional awards				0

Earnings Per Share - Additional Information (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive securities excluded from computation of earnings per share, amount	0	0	12,415	0
Performance Shares \| Initial Performance Vesting Period
Share-based compensation arrangement by share-based payment award, award vesting period			2 years

Earnings Per Share - Schedule of Dilutive Effect of Stock Options RSUs and PSAs (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net Income	$ 13,617	$ 11,937	$ 26,034	$ 22,114
Basic	18,806	18,775	18,738	18,840
Dilutive effect of stock options, RSUs, and performance shares	403	311	470	412
Weighted-average number of diluted shares outstanding during the period	19,209	19,086	19,208	19,252
Basic	$ 0.72	$ 0.64	$ 1.39	$ 1.17
Diluted	$ 0.71	$ 0.63	$ 1.36	$ 1.15

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Share Repurchase Program - Additional Information (Details)	Jun. 30, 2018 USD ($)
Equity [Abstract]
Stock repurchase program, authorized amount	$ 100,000,000
Stock repurchase program, remaining authorized repurchase amount	$ 95,000,000
Line of credit facility, conditions for the elimination of limits on shares repurchases, leverage ratio	3.25

Subsequent Events - Additional Information (Details) - Subsequent Event	Aug. 02, 2018 $ / shares
Subsequent Event [Line Items]
Dividend declaration date	Aug. 02, 2018
Cash dividend per share	$ 0.14
Dividend payment date	Oct. 16, 2018
Dividend close of record date	Sep. 07, 2018

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	Jun. 10, 2017	Jun. 30, 2018
Loss Contingencies [Line Items]
Community development related to claim		$ 220.2
OCD vs ICF Emergency
Loss Contingencies [Line Items]
Loss contingency damages sought value	$ 200.8
Road Home Contract
Loss Contingencies [Line Items]
Contract term, period	3 years
Contract award, value	$ 912.0