v3.26.1
Revenue - Disaggregation of Revenue (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation Of Revenue [Line Items]        
Revenue from clients $ 474,495 $ 476,155 $ 911,995 $ 963,773
Time-and-Materials        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 202,311 206,710 394,296 415,702
Fixed-Price        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 245,423 238,456 459,168 476,577
Cost-Based        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 26,761 30,989 58,531 71,494
U.S. Federal Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 184,913 204,389 367,356 443,551
U.S. State and Local Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 84,049 85,682 161,097 162,793
International Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 39,521 29,259 71,347 56,348
Total Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients 308,483 319,330 599,800 662,692
Commercial        
Disaggregation Of Revenue [Line Items]        
Revenue from clients $ 166,012 $ 156,825 $ 312,195 $ 301,081
Customer Concentration Risk | Revenue from Contract with Customer        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 100.00% 100.00% 100.00% 100.00%
Customer Concentration Risk | Revenue from Contract with Customer | Time-and-Materials        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 43.00% 43.00% 43.00% 43.00%
Customer Concentration Risk | Revenue from Contract with Customer | Fixed-Price        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 52.00% 50.00% 50.00% 50.00%
Customer Concentration Risk | Revenue from Contract with Customer | Cost-Based        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 5.00% 7.00% 7.00% 7.00%
Customer Concentration Risk | Revenue from Contract with Customer | U.S. Federal Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 39.00% 43.00% 40.00% 46.00%
Customer Concentration Risk | Revenue from Contract with Customer | U.S. State and Local Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 18.00% 18.00% 18.00% 17.00%
Customer Concentration Risk | Revenue from Contract with Customer | International Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 8.00% 6.00% 8.00% 6.00%
Customer Concentration Risk | Revenue from Contract with Customer | Total Government        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 65.00% 67.00% 66.00% 69.00%
Customer Concentration Risk | Revenue from Contract with Customer | Commercial        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 35.00% 33.00% 34.00% 31.00%
Energy, Environment, Infrastructure, and Disaster Recovery        
Disaggregation Of Revenue [Line Items]        
Revenue from clients $ 251,112 $ 248,504 $ 483,031 $ 487,034
Energy, Environment, Infrastructure, and Disaster Recovery | Customer Concentration Risk | Revenue from Contract with Customer        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 53.00% 52.00% 53.00% 51.00%
Health and Social Programs        
Disaggregation Of Revenue [Line Items]        
Revenue from clients $ 158,719 $ 158,625 $ 301,319 $ 328,059
Health and Social Programs | Customer Concentration Risk | Revenue from Contract with Customer        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 33.00% 33.00% 33.00% 34.00%
Security and Other Civilian & Commercial        
Disaggregation Of Revenue [Line Items]        
Revenue from clients $ 64,664 $ 69,026 $ 127,645 $ 148,680
Security and Other Civilian & Commercial | Customer Concentration Risk | Revenue from Contract with Customer        
Disaggregation Of Revenue [Line Items]        
Revenue from clients, Percent 14.00% 15.00% 14.00% 15.00%