Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Lease cost
Operating lease cost	$ 2,009	$ 959
Sublease income	(29)	(29)
Total lease cost	1,980	930
Operating cash flows	1,767	873
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 1,696	$ 4,650
Weighted-average discount rate	6.40%	6.60%