Restructuring Costs - Summary of Activity and Estimated Timing of Future Payouts for Accrued Restructuring Costs (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Restructuring Reserve [Roll Forward]
Restructuring costs	$ 1,376	$ 1,376
Non-cash asset impairment charge	(375)	(375)
Cash payments	(340)	(340)
Ending Balance	661	661
Estimated timing of future payments:
Remainder of 2019	573	573
2020	88	88
Total stock-based compensation expense	$ 661	$ 661