Revenue Recognition (Tables)

12 Months Ended

Dec. 31, 2018

Disaggregation Of Revenue [Abstract]

Disaggregation of Revenue

Disaggregation of Revenue

	Year ended December 31,
	2018		2017		2016
Client Markets:
Energy, environment, and infrastructure	$	565,125	$	487,001	$	457,992
Health, education, and social programs		535,314		518,675		508,903
Safety and security		111,072		102,645		98,358
Consumer and financial		126,462		120,841		119,844
Total	$	1,337,973	$	1,229,162	$	1,185,097

	Year ended December 31,
	2018		2017		2016
Client Type:
U.S. federal government	$	543,918	$	550,794	$	563,498
U.S. state and local government		185,130		127,797		132,287
International government		122,293		91,318		75,636
Total Government		851,341		769,909		771,421
Commercial		486,632		459,253		413,676
Total	$	1,337,973	$	1,229,162	$	1,185,097

	Year ended December 31,
	2018		2017		2016
Contract Mix:
Time-and-materials	$	581,965	$	529,606	$	511,747
Fixed-price		526,728		480,584		456,065
Cost-based		229,280		218,972		217,285
Total	$	1,337,973	$	1,229,162	$	1,185,097

Schedule of Contract Balances and Changes in Contract Balances

Contract Balances:

	December 31, 2018			At date of adoption			Change
Contract assets	$	126,688		$	123,197		$	3,491
Contract liabilities		(33,494	)		(38,571	)		5,077
Net contract assets (liabilities)	$	93,194		$	84,626		$	8,568