Property and Equipment, Net - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 143,055	$ 109,963
Less: Accumulated depreciation	(84,433)	(72,119)
Property and equipment, net	58,622	37,844
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	88,161	64,727
Office equipment, including data processing equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	20,974	20,044
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	11,785	9,874
Furniture, fixtures, and equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	11,421	7,911
Projects in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 10,714	$ 7,407