Fair Value - Changes in Fair Value of Level 3 Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Preferred shares, derivative liability, Beginning Balance	$ 0	$ 29,470
Preferred shares, derivative liability, Conversions	0	0
Preferred shares, derivative liability, Remeasurement included in earnings	0	(1,212)
Preferred shares, derivative liability, Ending Balance	$ 0	$ 28,258