Leases - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Operating Leased Assets [Line Items]
Operating lease, right of use asset	$ 81,543		$ 85,538
Right of use asset obtained in exchange for operating lease liability	700	$ 5,000
UNITED STATES
Operating Leased Assets [Line Items]
Operating lease, right of use asset	68,700		71,000
Operating lease, liability	94,600		97,500
UNITED STATES | Northern Virginia Office Space
Operating Leased Assets [Line Items]
Operating lease, right of use asset	65,100		66,900
Operating lease, liability	90,900		93,300
Non-US
Operating Leased Assets [Line Items]
Operating lease, right of use asset	12,800		14,500
Operating lease, liability	$ 13,700		$ 15,500