Revenue Recognition (Tables)

3 Months Ended

Mar. 31, 2021

Revenue From Contract With Customer [Abstract]

Disaggregation of Revenue

Disaggregation of Revenue

Changes in the three months ended March 31, 2021 compared to the prior year period were primarily from an increase of revenue in the energy, environment, and infrastructure client market and the health, education, and social programs client market as a result of  U.S. government clients and international government clients, partially offset by decreases in revenue from the consumer and financial markets primarily as a result of commercial clients.

	Three Months Ended March 31,
	2021					2020
	Dollars		Percent			Dollars		Percent
Client Markets:
Energy, environment, and infrastructure	$	164,492		43	%	$	148,961		42	%
Health, education, and social programs		157,765		42	%		151,352		42	%
Safety and security		31,198		8	%		30,301		8	%
Consumer and financial services		25,023		7	%		27,624		8	%
Total	$	378,478		100	%	$	358,238		100	%

	Three Months Ended March 31,
	2021					2020
	Dollars		Percent			Dollars		Percent
Client Type:
U.S. federal government	$	175,913		46	%	$	155,604		43	%
U.S. state and local government		57,152		15	%		60,893		17	%
International government		37,061		10	%		22,801		7	%
Total Government		270,126		71	%		239,298		67	%
Commercial		108,352		29	%		118,940		33	%
Total	$	378,478		100	%	$	358,238		100	%

	Three Months Ended March 31,
	2021					2020
	Dollars		Percent			Dollars		Percent
Contract Mix:
Time-and-materials	$	160,009		42	%	$	168,070		47	%
Fixed price		147,296		39	%		133,204		37	%
Cost-based		71,173		19	%		56,964		16	%
Total	$	378,478		100	%	$	358,238		100	%

Schedule of Contract Balances and Changes in Contract Balances

Contract Balances:

Contract assets consist primarily of unbilled amounts resulting from long-term contracts when revenue recognized exceeds the amount billed often 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 net contract assets (liabilities) as of March 31, 2021 increased by $19.2 million as compared to December 31, 2020. The increase in net contract assets (liabilities) is primarily due to an increase in work in the energy, environmental, and infrastructure client market and health, education, and social programs client market, offset by decreases in work in the consumer and financial market. There were no material changes to contract balances due to impairments during the period. During the three months ended March 31, 2021 and 2020, the Company recognized $15.1 million and $17.3 million in revenue related to the contract liabilities balance at December 31, 2020 and 2019, respectively.

	March 31, 2021			December 31, 2020			$ Change			% Change
Contract assets	$	164,155		$	143,369		$	20,786			14.5	%
Contract liabilities		(43,589	)		(42,050	)		(1,539	)		3.7	%
Net contract assets (liabilities)	$	120,566		$	101,319		$	19,247			19.0	%