Leases - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Operating Leased Assets [Line Items]
Operating lease, right of use asset	$ 82,690		$ 85,538
Right of use asset obtained in exchange for operating lease liability	0	$ 1,000
UNITED STATES
Operating Leased Assets [Line Items]
Operating lease, right of use asset	69,900		71,000
Operating lease, liability	96,100		97,500
UNITED STATES | Northern Virginia Office Space
Operating Leased Assets [Line Items]
Operating lease, right of use asset	66,000		66,900
Operating lease, liability	92,100		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