Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	$ 119,189	$ 113,938
Less: accumulated depreciation	(82,861)	(79,233)
Total	36,328	34,705
Computer Equipment And Software [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	105,478	100,392
Furniture, Equipment and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	$ 13,711	$ 13,546