Property And Equipment (Property And Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 289,164	$ 233,829
Less: Accumulated depreciation and amortization	(190,351)	(154,056)
Total property and equipment, net	98,813	79,773
Computers and related equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	272,067	215,631
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,391	2,035
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 14,706	$ 16,163