Properties and Equipment Property and equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 107,048	$ 103,669
Accumulated depreciation	(88,859)	(84,941)
Property and equipment, net	18,189	18,728
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	49,755	49,488
Equipment and Furniture [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	21,451	20,485
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	24,827	25,129
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 11,015	$ 8,567