Property and Equipment, Net - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 109,963	$ 92,227
Accumulated depreciation	(72,119)	(59,929)
Property and equipment, net	37,844	32,298
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	64,727	53,349
Office equipment, including data processing equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	20,044	18,550
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	9,874	7,092
Furniture, fixtures, and equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	7,911	6,450
Projects in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7,407	$ 6,786