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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Summary of Significant Accounting Policies
Net loss	$ (13,797)	$ (30,616)	$ (17,836)	$ (33,672)
Weighted average number of shares - basic and diluted	42,604,189	42,403,140	42,603,315	42,403,084