Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Lease cost
Operating lease cost	$ 1,646	$ 1,006	$ 4,405	$ 2,874
Sublease income	(29)	(29)	(87)	(87)
Total lease cost	1,617	977	4,318	2,787
Operating cash flows	1,621	811	3,879	2,410
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 155	$ 740	$ 5,213	$ 1,353
Weighted-average discount rate	6.60%	6.60%	6.60%	6.60%