Goodwill and Intangible Assets, net - Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Beginning balance	$ 409,588	$ 408,025
Acquisitions	181,080	0
Other	0	1,563
Ending balance	590,668	409,588
GMS
Goodwill [Roll Forward]
Beginning balance	208,593	208,593
Acquisitions	0	0
Other	0	0
Ending balance	208,593	208,593
NSS
Goodwill [Roll Forward]
Beginning balance	200,995	199,432
Acquisitions	181,080	0
Other	0	1,563
Ending balance	$ 382,075	$ 200,995