Annual report [Section 13 and 15(d), not S-K Item 405]

Revenue Recognition - Disaggregation of Revenue (Details)

v3.25.3
Revenue Recognition - Disaggregation of Revenue (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2023
Disaggregation of Revenue [Line Items]      
Revenue $ 5,431,276 $ 5,306,197 $ 4,904,728
New York state government agencies      
Disaggregation of Revenue [Line Items]      
Revenue $ 610,755 $ 647,349 $ 525,051
New York state government agencies | Revenue Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 11.20% 12.20% 10.70%
Other U.S. state government agencies      
Disaggregation of Revenue [Line Items]      
Revenue $ 1,153,928 $ 1,255,181 $ 1,275,763
Other U.S. state government agencies | Revenue Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 21.20% 23.70% 26.00%
Total U.S. state government agencies      
Disaggregation of Revenue [Line Items]      
Revenue $ 1,764,683 $ 1,902,530 $ 1,800,814
U.S. federal government agencies      
Disaggregation of Revenue [Line Items]      
Revenue $ 2,995,821 $ 2,674,014 $ 2,344,863
U.S. federal government agencies | Revenue Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 55.20% 50.40% 47.80%
International government agencies      
Disaggregation of Revenue [Line Items]      
Revenue $ 590,798 $ 642,222 $ 663,044
International government agencies | Revenue Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 10.90% 12.10% 13.50%
Other, including local municipalities and commercial customers      
Disaggregation of Revenue [Line Items]      
Revenue $ 79,974 $ 87,431 $ 96,007
Other, including local municipalities and commercial customers | Revenue Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 1.50% 1.60% 2.00%
Performance-based      
Disaggregation of Revenue [Line Items]      
Revenue $ 2,954,395 $ 2,939,536 $ 2,425,597
Performance-based | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 54.40% 55.40% 49.50%
Cost-plus      
Disaggregation of Revenue [Line Items]      
Revenue $ 1,316,646 $ 1,247,202 $ 1,238,574
Cost-plus | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 24.20% 23.50% 25.30%
Fixed price      
Disaggregation of Revenue [Line Items]      
Revenue $ 712,878 $ 686,555 $ 717,167
Fixed price | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 13.10% 12.90% 14.60%
Time and materials      
Disaggregation of Revenue [Line Items]      
Revenue $ 447,357 $ 432,904 $ 523,390
Time and materials | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 8.20% 8.20% 10.70%
Program Operations      
Disaggregation of Revenue [Line Items]      
Revenue $ 2,650,764 $ 2,570,494 $ 2,500,678
Program Operations | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 48.80% 48.40% 51.00%
Clinical Services      
Disaggregation of Revenue [Line Items]      
Revenue $ 2,100,943 $ 1,891,292 $ 1,486,040
Clinical Services | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 38.70% 35.60% 30.30%
Employment & Other      
Disaggregation of Revenue [Line Items]      
Revenue $ 354,835 $ 469,304 $ 520,981
Employment & Other | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 6.50% 8.80% 10.60%
Technology Solutions      
Disaggregation of Revenue [Line Items]      
Revenue $ 324,734 $ 375,107 $ 397,029
Technology Solutions | Revenue Benchmark | Contract Concentration Risk      
Disaggregation of Revenue [Line Items]      
Revenue in % 6.00% 7.10% 8.10%