Income Taxes - Components of income tax provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ (157)	$ 0	$ 0
State	(1,350)	(2,429)	(989)
Deferred:
Federal	0	0	0
State	0	0	0
Total provision	$ (1,507)	$ (2,429)	$ (989)