Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment, net
Property, Plant and Equipment, Gross	$ 359,836	$ 273,541
Less: accumulated depreciation and amortization	(161,814)	(142,781)
Property and equipment, net	198,022	130,760
Lease incentives	24,700	10,400
Amortization of tenant improvements reimbursement	500	100
Depreciation expense	29,000	23,700	$ 23,300
Land
Property and Equipment, net
Property, Plant and Equipment, Gross	12,243	6,248
Buildings and improvements
Property and Equipment, net
Property, Plant and Equipment, Gross	17,791	7,669
Leasehold improvements - inclusive of right to use assets
Property and Equipment, net
Property, Plant and Equipment, Gross	106,681	92,168
Furniture and equipment
Property and Equipment, net
Property, Plant and Equipment, Gross	115,429	91,449
Software
Property and Equipment, net
Property, Plant and Equipment, Gross	73,310	71,509
Systems development and construction in progress
Property and Equipment, net
Property, Plant and Equipment, Gross	$ 34,382	$ 4,498