v3.26.1
Revenue Recognition - Schedule of Disaggregation of Revenue (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Total revenue $ 1,278,971 $ 1,348,400 $ 3,929,984 $ 4,112,861
New York state government agencies        
Disaggregation of Revenue [Line Items]        
Total revenue $ 148,067 $ 148,408 $ 445,548 $ 466,053
New York state government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 11.60% 11.00% 11.30% 11.30%
Other U.S. state government agencies        
Disaggregation of Revenue [Line Items]        
Total revenue $ 275,793 $ 291,312 $ 817,052 $ 869,561
Other U.S. state government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 21.60% 21.60% 20.80% 21.10%
Total U.S. state government agencies        
Disaggregation of Revenue [Line Items]        
Total revenue $ 423,860 $ 439,720 $ 1,262,600 $ 1,335,614
U.S. federal government agencies        
Disaggregation of Revenue [Line Items]        
Total revenue $ 701,932 $ 743,058 $ 2,204,623 $ 2,267,078
U.S. federal government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 54.90% 55.10% 56.10% 55.10%
International government agencies        
Disaggregation of Revenue [Line Items]        
Total revenue $ 137,462 $ 146,018 $ 413,321 $ 451,608
International government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 10.70% 10.80% 10.50% 11.00%
Other, including local municipalities and commercial customers        
Disaggregation of Revenue [Line Items]        
Total revenue $ 15,717 $ 19,604 $ 49,440 $ 58,561
Other, including local municipalities and commercial customers | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 1.20% 1.50% 1.30% 1.40%
Performance-based        
Disaggregation of Revenue [Line Items]        
Total revenue $ 755,826 $ 761,428 $ 2,209,585 $ 2,193,605
Performance-based | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 59.10% 56.50% 56.20% 53.30%
Cost-plus        
Disaggregation of Revenue [Line Items]        
Total revenue $ 303,486 $ 301,385 $ 1,033,798 $ 1,020,311
Cost-plus | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 23.70% 22.40% 26.30% 24.80%
Fixed price        
Disaggregation of Revenue [Line Items]        
Total revenue $ 155,200 $ 180,390 $ 489,327 $ 540,078
Fixed price | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 12.10% 13.40% 12.50% 13.10%
Time and materials        
Disaggregation of Revenue [Line Items]        
Total revenue $ 64,459 $ 105,197 $ 197,274 $ 358,867
Time and materials | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 5.00% 7.80% 5.00% 8.70%
Program Operations        
Disaggregation of Revenue [Line Items]        
Total revenue $ 602,807 $ 626,981 $ 1,924,106 $ 2,045,720
Program Operations | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 47.10% 46.50% 49.00% 49.70%
Clinical Services        
Disaggregation of Revenue [Line Items]        
Total revenue $ 553,075 $ 560,360 $ 1,607,602 $ 1,535,849
Clinical Services | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 43.20% 41.60% 40.90% 37.30%
Employment & Other        
Disaggregation of Revenue [Line Items]        
Total revenue $ 55,852 $ 81,906 $ 186,025 $ 274,513
Employment & Other | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 4.40% 6.10% 4.70% 6.70%
Technology Solutions        
Disaggregation of Revenue [Line Items]        
Total revenue $ 67,237 $ 79,153 $ 212,251 $ 256,779
Technology Solutions | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Total revenue (as a percent) 5.30% 5.90% 5.40% 6.20%