Revenue Recognition (Tables)

12 Months Ended

Dec. 31, 2020

Revenue From Contract With Customer [Abstract]

Disaggregation of Revenue

Disaggregation of Revenue

	Year ended December 31,
	2020		2019		2018
Client Markets:
Energy, environment, and infrastructure	$	616,296	$	663,799	$	564,736
Health, education, and social programs		670,618		567,351		535,578
Safety and security		117,979		118,279		111,660
Consumer and financial		101,982		129,096		125,999
Total	$	1,506,875	$	1,478,525	$	1,337,973

	Year ended December 31,
	2020		2019		2018
Client Type:
U.S. federal government	$	666,961	$	560,953	$	546,050
U.S. state and local government		222,730		279,833		183,900
International government		95,734		122,125		122,186
Total Government		985,425		962,911		852,136
Commercial		521,450		515,614		485,837
Total	$	1,506,875	$	1,478,525	$	1,337,973

	Year ended December 31,
	2020		2019		2018
Contract Mix:
Time-and-materials	$	749,844	$	700,980	$	581,446
Fixed-price		529,157		566,299		526,751
Cost-based		227,874		211,246		229,776
Total	$	1,506,875	$	1,478,525	$	1,337,973

Schedule of Contract Balances and Changes in Contract Balances

Contract Balances:

	December 31, 2020			December 31, 2019			Change
Contract assets	$	143,369		$	142,337		$	1,032
Contract liabilities		(42,050	)		(37,413	)		(4,637	)
Net contract assets	$	101,319		$	104,924		$	(3,605	)