Supplemental Consolidated Balance Sheet Information (Property and Equipment, Net) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 179,512	$ 188,941
Less: accumulated depreciation and amortization	(116,840)	(125,916)
Property and equipment, net	62,672	63,025
Furniture, Fixtures and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	53,309	55,619
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	79,188	86,225
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 47,015	$ 47,097