Quarterly report pursuant to Section 13 or 15(d)

Revenue Recognition - Disaggregation of Revenue (Details)

v3.22.4
Revenue Recognition - Disaggregation of Revenue (Details) - USD ($)
$ in Thousands
 3 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Disaggregation of Revenue [Line Items]    
Revenue $ 1,249,246 $ 1,150,876
U. S. federal government agencies    
Disaggregation of Revenue [Line Items]    
Revenue $ 603,918 $ 564,094
U. S. federal government agencies | Revenue Benchmark | Customer Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 48.30% 49.00%
U.S. state government agencies    
Disaggregation of Revenue [Line Items]    
Revenue $ 437,362 $ 371,547
U.S. state government agencies | Revenue Benchmark | Customer Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 35.00% 32.30%
International government agencies    
Disaggregation of Revenue [Line Items]    
Revenue $ 181,760 $ 171,375
International government agencies | Revenue Benchmark | Customer Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 14.50% 14.90%
Other, including local municipalities and commercial customers    
Disaggregation of Revenue [Line Items]    
Revenue $ 26,206 $ 43,860
Other, including local municipalities and commercial customers | Revenue Benchmark | Customer Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 2.10% 3.80%
Performance-based    
Disaggregation of Revenue [Line Items]    
Revenue $ 569,217 $ 490,956
Performance-based | Revenue Benchmark | Contract Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 45.60% 42.70%
Cost-plus    
Disaggregation of Revenue [Line Items]    
Revenue $ 347,319 $ 340,081
Cost-plus | Revenue Benchmark | Contract Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 27.80% 29.50%
Fixed price    
Disaggregation of Revenue [Line Items]    
Revenue $ 175,073 $ 151,505
Fixed price | Revenue Benchmark | Contract Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 14.00% 13.20%
Time and materials    
Disaggregation of Revenue [Line Items]    
Revenue $ 157,637 $ 168,334
Time and materials | Revenue Benchmark | Contract Concentration Risk    
Disaggregation of Revenue [Line Items]    
Revenue in % 12.60% 14.60%