Segment Information - Summary of Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 879,356	$ 979,459	$ 1,754,053	$ 1,950,452
Federal Solution Segment
Segment Reporting Information [Line Items]
Total revenue	442,675	482,210	894,744	959,781
Critical Infrastructure
Segment Reporting Information [Line Items]
Total revenue	$ 436,681	$ 497,249	$ 859,309	$ 990,671