Quarterly report pursuant to Section 13 or 15(d)

Revenue Recognition - Disaggregation of Revenue (Details)

v3.22.2
Revenue Recognition - Disaggregation of Revenue (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2022
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2021
Disaggregation of Revenue [Line Items]        
Revenue $ 1,125,785 $ 1,243,520 $ 3,453,987 $ 3,148,354
United States        
Disaggregation of Revenue [Line Items]        
Revenue $ 924,839 $ 1,053,940 $ 2,864,492 $ 2,622,469
United States | Revenue Benchmark | Geographic Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 82.20% 84.80% 83.00% 83.30%
United Kingdom        
Disaggregation of Revenue [Line Items]        
Revenue $ 109,776 $ 74,109 $ 303,481 $ 211,777
United Kingdom | Revenue Benchmark | Geographic Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 9.70% 6.00% 8.80% 6.70%
Australia        
Disaggregation of Revenue [Line Items]        
Revenue $ 43,594 $ 65,283 $ 143,078 $ 192,161
Australia | Revenue Benchmark | Geographic Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 3.90% 5.20% 4.10% 6.10%
Rest of world        
Disaggregation of Revenue [Line Items]        
Revenue $ 47,576 $ 50,188 $ 142,936 $ 121,947
Rest of world | Revenue Benchmark | Geographic Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 4.20% 4.00% 4.10% 3.90%
U.S. state government agencies        
Disaggregation of Revenue [Line Items]        
Revenue $ 401,042 $ 431,987 $ 1,183,876 $ 1,265,798
U.S. state government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 35.70% 34.70% 34.30% 40.20%
U.S. federal government agencies        
Disaggregation of Revenue [Line Items]        
Revenue $ 507,047 $ 594,771 $ 1,624,848 $ 1,288,213
U.S. federal government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 45.00% 47.80% 47.00% 40.90%
International government agencies        
Disaggregation of Revenue [Line Items]        
Revenue $ 191,753 $ 180,049 $ 557,928 $ 499,091
International government agencies | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 17.00% 14.50% 16.20% 15.90%
Other, including local municipalities and commercial customers        
Disaggregation of Revenue [Line Items]        
Revenue $ 25,943 $ 36,713 $ 87,335 $ 95,252
Other, including local municipalities and commercial customers | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 2.30% 3.00% 2.50% 3.00%
Performance-based        
Disaggregation of Revenue [Line Items]        
Revenue $ 520,202 $ 389,800 $ 1,527,368 $ 1,033,509
Performance-based | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 46.20% 31.30% 44.20% 32.80%
Cost-plus        
Disaggregation of Revenue [Line Items]        
Revenue $ 282,578 $ 282,808 $ 945,482 $ 953,373
Cost-plus | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 25.10% 22.70% 27.40% 30.30%
Fixed price        
Disaggregation of Revenue [Line Items]        
Revenue $ 160,219 $ 146,175 $ 470,591 $ 413,296
Fixed price | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 14.20% 11.80% 13.60% 13.10%
Time and materials        
Disaggregation of Revenue [Line Items]        
Revenue $ 162,786 $ 424,737 $ 510,546 $ 748,176
Time and materials | Revenue Benchmark | Contract Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue in % 14.50% 34.20% 14.80% 23.80%