Revenue Recognition (Tables)

6 Months Ended

Jun. 30, 2020

Revenue From Contract With Customer [Abstract]

Changes in the three and six months ended June 30, 2020 compared to the prior year period were primarily from the increase of revenue in the health, education, and social programs client market as a result of additional work performed for U.S. government clients, including the ITG acquisition, offset by decreases in revenue from the commercial clients primarily in the consumer and financial services and health, education and social programs markets and decreases in the U.S. state and local clients in the energy, environment, and infrastructure markets. Similarly, for the three and six months ended June 30, 2020 revenue from time-and-materials and cost-based contracts increased while revenue from fixed price contracts decreased compared to the prior year period.

	Three Months Ended June 30,										Six Months Ended June 30,
	2020					2019					2020					2019
	Dollars		Percent			Dollars		Percent			Dollars		Percent			Dollars		Percent
Client Markets:
Energy, environment, and infrastructure	$	151,481		43	%	$	166,520		45	%	$	303,839		43	%	$	320,035		45	%
Health, education, and social programs		148,528		42	%		134,346		37	%		291,114		41	%		256,255		36	%
Safety and security		31,440		9	%		30,030		8	%		63,025		9	%		59,581		9	%
Consumer and financial services		22,538		6	%		35,821		10	%		54,247		7	%		72,100		10	%
Total	$	353,987		100	%	$	366,717		100	%	$	712,225		100	%	$	707,971		100	%

	Three Months Ended										Six Months Ended June 30,
	June 30, 2020					June 30, 2019					2020					2019
	Dollars		Percent			Dollars		Percent			Dollars		Percent			Dollars		Percent
Client Type:
U.S. federal government	$	170,748		48	%	$	141,253		38	%	$	326,318		46	%	$	273,465		39	%
U.S. state and local government		57,982		17	%		73,101		20	%		119,288		17	%		138,928		20	%
International government		18,098		5	%		31,617		9	%		41,190		6	%		58,751		8	%
Total Government		246,828		70	%		245,971		67	%		486,796		69	%		471,144		67	%
Commercial		107,159		30	%		120,746		33	%		225,429		31	%		236,827		33	%
Total	$	353,987		100	%	$	366,717		100	%	$	712,225		100	%	$	707,971		100	%

	Three Months Ended										Six Months Ended June 30,
	June 30, 2020					June 30, 2019					2020					2019
	Dollars		Percent			Dollars		Percent			Dollars		Percent			Dollars		Percent
Contract Mix:
Time-and-materials	$	168,489		48	%	$	167,009		46	%	$	336,639		47	%	$	322,191		45	%
Fixed price		123,970		35	%		146,967		40	%		257,122		36	%		281,416		40	%
Cost-based		61,528		17	%		52,741		14	%		118,464		17	%		104,364		15	%
Total	$	353,987		100	%	$	366,717		100	%	$	712,225		100	%	$	707,971		100	%

Schedule of Contract Balances and Changes in Contract Balances

Contract Balances:

	June 30, 2020			December 31, 2019			$ Change		% Change
Contract assets	$	150,577		$	142,337		$	8,240		5.8	%
Contract liabilities		(30,135	)		(37,413	)		7,278		(19.5	%)
Net contract assets (liabilities)	$	120,442		$	104,924		$	15,518		14.8	%