Revenue Recognition (Tables)

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

Disaggregation of Revenue

	Year ended December 31,
	2022		2021		2020
Client Markets:
Energy, environment, and infrastructure	$	664,996	$	653,080	$	609,358
Health, education, and social programs		906,081		677,736		677,454
Safety and security		129,357		115,659		120,599
Consumer and financial		79,530		106,573		99,464
Total	$	1,779,964	$	1,553,048	$	1,506,875

	Year ended December 31,
	2022		2021		2020
Client Type:
U.S. federal government	$	980,406	$	735,104	$	666,968
U.S. state and local government		260,562		235,353		219,507
International government		102,808		139,237		93,581
Government		1,343,776		1,109,694		980,056
Commercial		436,188		443,354		526,819
Total	$	1,779,964	$	1,553,048	$	1,506,875

	Year ended December 31,
	2022		2021		2020
Contract Mix:
Time-and-materials	$	713,581	$	633,152	$	732,365
Fixed-price		802,804		645,761		536,903
Cost-based		263,579		274,135		237,607
Total	$	1,779,964	$	1,553,048	$	1,506,875

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 December 31, 2022 and December 31, 2021:

	December 31, 2022			December 31, 2021			Change
Contract assets	$	169,088		$	137,867		$	31,221
Contract liabilities		(25,773	)		(39,665	)		13,892
Net contract assets (liabilities)	$	143,315		$	98,202		$	45,113

The net contract assets (liabilities) as of December 31, 2022 increased by $45.1 million as compared to December 31, 2021, primarily due to the timing difference between the performance of services and billings to and payments from customers. There were no material changes to contract balances due to impairments or credit losses during the period. During the years ended December 31, 2022 and 2021, the Company recognized $27.4 million and $22.7 million in revenue related to the contract liabilities balance at December 31, 2021 and 2020, respectively.