Commitments and Contingencies - Future Minimum Payments Under Leases (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Capital Leases
2018	$ 252
2019	252
2020	60
2021	0
2022	0
Total minimum lease payments	564
Less: amount representing interest	(32)
Present value of capital lease obligations	532
Less: current portion	(230)
Long-term portion of capital leases	302
Operating leases
2018	3,185
2019	3,280
2020	712
2021	490
2022	41
Total minimum payments	7,708
Total future minimum sublease rentals to be received under noncancellable subleases	$ 1,200