Fixed Assets - Fixed Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 408,690	$ 401,116
Less: Accumulated depreciation and amortization	(320,351)	(279,203)
Fixed assets, net	88,339	121,913
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 344,127	332,826
Computer Equipment and Software [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful life (in years)	3 years
Computer Equipment and Software [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful life (in years)	10 years
Facility Furniture, Fixtures and Equipment [Member]
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 24,704	21,300
Facility Furniture, Fixtures and Equipment [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful life (in years)	5 years
Facility Furniture, Fixtures and Equipment [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful life (in years)	7 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 39,335	37,555
Estimated useful life (in years)	Shorter of 7 years or life of lease
Assets Under Finance Lease [Member]
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 524	9,435
Less: Accumulated depreciation and amortization	$ (400)	$ (7,300)
Assets Under Finance Lease [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful life (in years)	1 year
Assets Under Finance Lease [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful life (in years)	3 years