Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Total property and equipment	$ 47,179	$ 38,855
Less accumulated depreciation and amortization	(20,155)	(14,929)
Total	27,024	23,926
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	5,964	5,726
Purchased Software
Property Plant And Equipment [Line Items]
Total property and equipment	1,071	1,071
Capitalized Software Development Costs
Property Plant And Equipment [Line Items]
Total property and equipment	20,285	14,755
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	4,522	3,924
Leasehold Improvements and Other
Property Plant And Equipment [Line Items]
Total property and equipment	$ 15,337	$ 13,379