Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 996,713	$ 991,782
Less: accumulated depreciation	(549,054)	(542,583)
Property and equipment, net	447,659	449,199
Depreciation	83,900	82,200	$ 73,700
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,476	7,476
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,487	6,293
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	63,255	61,582
Capitalized software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	878,156	866,398
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,990	29,420
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,349	$ 20,613