Income Taxes - Provision for income taxes (income tax benefits) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018
Current:
Federal									$ (39)	$ 1,705
State									(66)	340
Total current									(105)	2,045
Deferred:
Federal									(844)	1,847
State									9	369
Total deferred									(835)	2,216
Income tax expense (benefit)	$ (1,232)	$ (376)	$ 96	$ 572	$ (171)	$ 3,712	$ 220	$ 500	$ (940)	$ 4,261