Revenue Recognition - Disaggregation of Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation Of Revenue [Line Items]
Revenue from clients	$ 1,779,964	$ 1,553,048	$ 1,506,875
Time-and-Materials
Disaggregation Of Revenue [Line Items]
Revenue from clients	713,581	633,152	732,365
Fixed-Price
Disaggregation Of Revenue [Line Items]
Revenue from clients	802,804	645,761	536,903
Cost-Based
Disaggregation Of Revenue [Line Items]
Revenue from clients	263,579	274,135	237,607
U.S. Federal Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	980,406	735,104	666,968
U.S. State and Local Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	260,562	235,353	219,507
International Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	102,808	139,237	93,581
Total Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	1,343,776	1,109,694	980,056
Commercial
Disaggregation Of Revenue [Line Items]
Revenue from clients	436,188	443,354	526,819
Energy, Environmental and Infrastructure
Disaggregation Of Revenue [Line Items]
Revenue from clients	664,996	653,080	609,358
Health, Education and Social Programs
Disaggregation Of Revenue [Line Items]
Revenue from clients	906,081	677,736	677,454
Safety and Security
Disaggregation Of Revenue [Line Items]
Revenue from clients	129,357	115,659	120,599
Consumer and Financial
Disaggregation Of Revenue [Line Items]
Revenue from clients	$ 79,530	$ 106,573	$ 99,464