Summary of Significant Accounting Policies - Summary of reconciliation of shares used to determine net (loss) income per share (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Summary of Significant Accounting Policies
Net income (loss)	$ 2,667	$ (13,880)	$ (15,169)	$ (47,552)
Weighted average number of shares - basic and diluted	42,618,391	42,530,476	42,608,396	42,445,926