Revenue Recognition (Tables)

9 Months Ended

Sep. 30, 2023

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

	Three Months Ended September 30,										Nine Months Ended September 30,
	2023					2022					2023					2022
	Dollars		Percent			Dollars		Percent			Dollars		Percent			Dollars		Percent
Client Markets:
Energy, environment, infrastructure, and disaster recovery	$	204,802		41	%	$	179,002		38	%	$	596,089		40	%	$	522,698		40	%
Health and social programs		210,501		42	%		197,225		42	%		620,198		42	%		511,312		39	%
Security and other civilian & commercial		86,216		17	%		91,550		20	%		268,599		18	%		270,345		21	%
Total	$	501,519		100	%	$	467,777		100	%	$	1,484,886		100	%	$	1,304,355		100	%

	Three Months Ended September 30,										Nine Months Ended September 30,
	2023					2022					2023					2022
	Dollars		Percent			Dollars		Percent			Dollars		Percent			Dollars		Percent
Client Type:
U.S. federal government	$	279,314		56	%	$	271,609		58	%	$	820,116		55	%	$	715,986		55	%
U.S. state and local government		76,393		15	%		64,910		14	%		232,274		16	%		194,778		15	%
International government		27,623		5	%		23,046		5	%		74,598		5	%		79,060		6	%
Total Government		383,330		76	%		359,565		77	%		1,126,988		76	%		989,824		76	%
Commercial		118,189		24	%		108,212		23	%		357,898		24	%		314,531		24	%
Total	$	501,519		100	%	$	467,777		100	%	$	1,484,886		100	%	$	1,304,355		100	%

	Three Months Ended September 30,										Nine Months Ended September 30,
	2023					2022					2023					2022
	Dollars		Percent			Dollars		Percent			Dollars		Percent			Dollars		Percent
Contract Mix:
Time-and-materials	$	206,646		41	%	$	188,772		40	%	$	615,859		41	%	$	523,661		40	%
Fixed-price		223,173		45	%		210,919		45	%		667,711		45	%		580,836		45	%
Cost-based		71,700		14	%		68,086		15	%		201,316		14	%		199,858		15	%
Total	$	501,519		100	%	$	467,777		100	%	$	1,484,886		100	%	$	1,304,355		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 following table summarizes the contract balances as of September 30, 2023 and December 31, 2022:

	September 30, 2023			December 31, 2022
Contract assets	$	209,267		$	169,088
Contract liabilities		(16,989	)		(25,773	)
Net contract assets (liabilities)	$	192,278		$	143,315