Income Taxes - Components of the company's income tax (provision) benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 388	$ (1,418)	$ (2,103)
State	39	523	(675)
Total current	427	(895)	(2,778)
Deferred:
Federal	(752)	3,722	777
State	(184)	118	80
Total deferred	(936)	3,840	857
Total (provision for) benefit from income taxes	(509)	2,945	(1,921)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Amount	$ 0	$ 0	$ 770