Leases - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Leased Assets [Line Items]
Operating lease, right of use asset	$ 73,597	$ 85,538
Operating lease, liability	95,141
Gain on partial lease termination	(2,820)	0	$ 0
UNITED STATES
Operating Leased Assets [Line Items]
Operating lease, right of use asset	62,200	71,000
Operating lease, liability	82,900	97,500
UNITED STATES | Northern Virginia Office Space
Operating Leased Assets [Line Items]
Operating lease, right of use asset	59,000	66,900
Operating lease, liability	$ 79,700	93,300
Lease term expiration date	Dec. 31, 2030
Lease option to extend, description	option for the Company to extend the term for an additional five or 10 consecutive years
Lease termination fees	$ 1,600
Reduction in right of use assets	4,200
Reduction in lease liability	7,000
Gain on partial lease termination	2,800
Non-US
Operating Leased Assets [Line Items]
Operating lease, right of use asset	11,400	14,500
Operating lease, liability	$ 12,200	$ 15,500
Minimum | UNITED STATES | Northern Virginia Office Space
Operating Leased Assets [Line Items]
Lease extension term	5 years
Maximum | UNITED STATES | Northern Virginia Office Space
Operating Leased Assets [Line Items]
Lease extension term	10 years