Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Lease cost
Operating lease cost	$ 1,444	$ 2,009
Sublease income	0	(29)
Total lease cost	1,444	1,980
Operating cash flows	1,223	1,767
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 78	$ 1,696
Weighted-average discount rate	7.30%	6.40%