Revenue Recognition (Tables)

12 Months Ended

Dec. 31, 2019

Revenue From Contract With Customer [Abstract]

Disaggregation of Revenue

Disaggregation of Revenue

	Year ended December 31,
	2019		2018		2017
Client Markets:
Energy, environment, and infrastructure	$	665,185	$	564,736	$	487,001
Health, education, and social programs		552,600		535,578		518,675
Safety and security		120,078		111,660		102,645
Consumer and financial		140,662		125,999		120,841
Total	$	1,478,525	$	1,337,973	$	1,229,162

	Year ended December 31,
	2019		2018		2017
Client Type:
U.S. federal government	$	561,022	$	546,050	$	550,794
U.S. state and local government		280,357		183,900		127,797
International government		122,307		122,186		91,318
Total Government		963,686		852,136		769,909
Commercial		514,839		485,837		459,253
Total	$	1,478,525	$	1,337,973	$	1,229,162

	Year ended December 31,
	2019		2018		2017
Contract Mix:
Time-and-materials	$	703,467	$	581,446	$	529,606
Fixed-price		562,985		526,751		480,584
Cost-based		212,073		229,776		218,972
Total	$	1,478,525	$	1,337,973	$	1,229,162

Schedule of Contract Balances and Changes in Contract Balances

Contract Balances:

	December 31, 2019			December 31, 2018			Change
Contract assets	$	142,337		$	126,688		$	15,649
Contract liabilities		(37,413	)		(33,494	)		(3,919	)
Net contract assets (liabilities)	$	104,924		$	93,194		$	11,730