Revenue Recognition - Disaggregation of Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation Of Revenue [Line Items]
Revenue from clients	$ 2,019,787	$ 1,963,238	$ 1,779,964
Time-and-Materials
Disaggregation Of Revenue [Line Items]
Revenue from clients	855,538	811,911	713,693
Fixed-Price
Disaggregation Of Revenue [Line Items]
Revenue from clients	932,351	886,200	802,568
Cost-Based
Disaggregation Of Revenue [Line Items]
Revenue from clients	231,898	265,127	263,703
U.S. Federal Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	1,087,349	1,084,047	980,746
U.S. State and Local Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	316,083	309,516	259,764
International Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	110,798	103,446	103,609
Total Government
Disaggregation Of Revenue [Line Items]
Revenue from clients	1,514,230	1,497,009	1,344,119
Commercial
Disaggregation Of Revenue [Line Items]
Revenue from clients	505,557	466,229	435,845
Energy, Environment, Infrastructure, and Disaster Recovery
Disaggregation Of Revenue [Line Items]
Revenue from clients	929,711	805,942	714,628
Health and Social Programs
Disaggregation Of Revenue [Line Items]
Revenue from clients	764,477	814,789	704,465
Security and Other Civilian & Commercial
Disaggregation Of Revenue [Line Items]
Revenue from clients	$ 325,599	$ 342,507	$ 360,871