| Disaggregation of Revenue | 
 By operating segment and service 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
 | 
Three Months Ended March 31, | 
 | 
Six Months Ended March 31, | 
 
| (in thousands) | 
 | 
2021 | 
 | 
2020 | 
 | 
2021 | 
 | 
2020 | 
 
| Program administration | 
 | 
$ | 
345,383  | 
 | 
 | 
$ | 
236,436  | 
 | 
 | 
$ | 
639,227  | 
 | 
 | 
$ | 
473,343  | 
 | 
 
| Assessments and appeals | 
 | 
35,416  | 
 | 
 | 
29,916  | 
 | 
 | 
68,031  | 
 | 
 | 
63,747  | 
 | 
 
| Workforce and children services | 
 | 
55,045  | 
 | 
 | 
28,734  | 
 | 
 | 
102,866  | 
 | 
 | 
58,120  | 
 | 
 
| Other | 
 | 
12,371  | 
 | 
 | 
13,612  | 
 | 
 | 
23,025  | 
 | 
 | 
25,769  | 
 | 
 
| Total U.S. Services | 
 | 
$ | 
448,215  | 
 | 
 | 
$ | 
308,698  | 
 | 
 | 
$ | 
833,149  | 
 | 
 | 
$ | 
620,979  | 
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Program administration | 
 | 
$ | 
226,322  | 
 | 
 | 
$ | 
304,367  | 
 | 
 | 
$ | 
554,112  | 
 | 
 | 
$ | 
586,055  | 
 | 
 
| Technology solutions | 
 | 
62,784  | 
 | 
 | 
44,508  | 
 | 
 | 
97,448  | 
 | 
 | 
88,114  | 
 | 
 
| Assessments and appeals | 
 | 
41,030  | 
 | 
 | 
44,516  | 
 | 
 | 
83,821  | 
 | 
 | 
85,793  | 
 | 
 
| Total U.S. Federal Services | 
 | 
$ | 
330,136  | 
 | 
 | 
$ | 
393,391  | 
 | 
 | 
$ | 
735,381  | 
 | 
 | 
$ | 
759,962  | 
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Workforce and children services | 
 | 
$ | 
97,971  | 
 | 
 | 
$ | 
34,683  | 
 | 
 | 
$ | 
175,433  | 
 | 
 | 
$ | 
91,922  | 
 | 
 
| Assessments and appeals | 
 | 
57,966  | 
 | 
 | 
62,286  | 
 | 
 | 
111,089  | 
 | 
 | 
124,929  | 
 | 
 
| Program administration | 
 | 
22,932  | 
 | 
 | 
16,945  | 
 | 
 | 
45,988  | 
 | 
 | 
34,039  | 
 | 
 
| Other | 
 | 
2,060  | 
 | 
 | 
2,132  | 
 | 
 | 
3,794  | 
 | 
 | 
4,533  | 
 | 
 
| Total Outside the U.S. | 
 | 
$ | 
180,929  | 
 | 
 | 
$ | 
116,046  | 
 | 
 | 
$ | 
336,304  | 
 | 
 | 
$ | 
255,423  | 
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Total revenue | 
 | 
$ | 
959,280  | 
 | 
 | 
$ | 
818,135  | 
 | 
 | 
$ | 
1,904,834  | 
 | 
 | 
$ | 
1,636,364  | 
 | 
 
  
By contract type 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
 | 
Three Months Ended March 31, | 
 | 
Six Months Ended March 31, | 
 
| (in thousands) | 
 | 
2021 | 
 | 
2020 | 
 | 
2021 | 
 | 
2020 | 
 
| Performance-based | 
 | 
$ | 
349,749  | 
 | 
 | 
$ | 
275,669  | 
 | 
 | 
$ | 
643,709  | 
 | 
 | 
$ | 
568,427  | 
 | 
 
| Cost-plus | 
 | 
286,082  | 
 | 
 | 
398,973  | 
 | 
 | 
670,565  | 
 | 
 | 
761,784  | 
 | 
 
| Fixed price | 
 | 
146,344  | 
 | 
 | 
100,504  | 
 | 
 | 
267,121  | 
 | 
 | 
219,720  | 
 | 
 
| Time and materials | 
 | 
177,105  | 
 | 
 | 
42,989  | 
 | 
 | 
323,439  | 
 | 
 | 
86,433  | 
 | 
 
| Total revenue | 
 | 
$ | 
959,280  | 
 | 
 | 
$ | 
818,135  | 
 | 
 | 
$ | 
1,904,834  | 
 | 
 | 
$ | 
1,636,364  | 
 | 
 
  
  
By customer type 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
 | 
Three Months Ended March 31, | 
 | 
Six Months Ended March 31, | 
 
| (in thousands) | 
 | 
2021 | 
 | 
2020 | 
 | 
2021 | 
 | 
2020 | 
 
| New York State government agencies | 
 | 
$ | 
111,911  | 
 | 
 | 
$ | 
100,222  | 
 | 
 | 
$ | 
187,267  | 
 | 
 | 
$ | 
197,445  | 
 | 
 
| Other U.S. state government agencies | 
 | 
333,786  | 
 | 
 | 
217,195  | 
 | 
 | 
646,544  | 
 | 
 | 
427,081  | 
 | 
 
| Total U.S. state government agencies | 
 | 
445,697  | 
 | 
 | 
317,417  | 
 | 
 | 
833,811  | 
 | 
 | 
624,526  | 
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| U.S. Federal Government agencies | 
 | 
307,870  | 
 | 
 | 
374,909  | 
 | 
 | 
693,442  | 
 | 
 | 
726,742  | 
 | 
 
| International government agencies | 
 | 
171,700  | 
 | 
 | 
107,460  | 
 | 
 | 
319,042  | 
 | 
 | 
238,276  | 
 | 
 
| Other, including local municipalities and commercial customers | 
 | 
34,013  | 
 | 
 | 
18,349  | 
 | 
 | 
58,539  | 
 | 
 | 
46,820  | 
 | 
 
| Total revenue | 
 | 
$ | 
959,280  | 
 | 
 | 
$ | 
818,135  | 
 | 
 | 
$ | 
1,904,834  | 
 | 
 | 
$ | 
1,636,364  | 
 | 
 
  
  
By geography 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
 | 
Three Months Ended March 31, | 
 | 
Six Months Ended March 31, | 
 
| (in thousands) | 
 | 
2021 | 
 | 
2020 | 
 | 
2021 | 
 | 
2020 | 
 
| United States | 
 | 
$ | 
778,350  | 
 | 
 | 
$ | 
702,089  | 
 | 
 | 
$ | 
1,568,529  | 
 | 
 | 
$ | 
1,380,941  | 
 | 
 
| United Kingdom | 
 | 
72,882  | 
 | 
 | 
63,722  | 
 | 
 | 
137,668  | 
 | 
 | 
136,724  | 
 | 
 
| Australia | 
 | 
70,947  | 
 | 
 | 
24,540  | 
 | 
 | 
126,878  | 
 | 
 | 
61,975  | 
 | 
 
| Rest of world | 
 | 
37,101  | 
 | 
 | 
27,784  | 
 | 
 | 
71,759  | 
 | 
 | 
56,724  | 
 | 
 
| Total revenue | 
 | 
$ | 
959,280  | 
 | 
 | 
$ | 
818,135  | 
 | 
 | 
$ | 
1,904,834  | 
 | 
 | 
$ | 
1,636,364  | 
 | 
 
  
 |