Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 32,361	$ 29,918
Less: Accumulated depreciation and amortization	(21,924)	(17,091)
Property and equipment, net	10,437	12,827
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	16,763	15,740
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,710	3,631
Furniture
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,534	1,561
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 9,354	$ 8,986