Property and Equipment, Net - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 102,073	$ 92,227
Accumulated depreciation	(65,939)	(59,929)
Property and equipment, net	36,134	32,298
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	54,131	53,349
Office equipment, including data processing equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	19,797	18,550
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	9,463	7,092
Furniture, fixtures, and equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,937	6,450
Projects in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 11,745	$ 6,786