Income Taxes - Components of tax (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal									$ 498	$ (515)	$ 0
State									134	(267)	720
Total current tax expense (benefit)									632	(782)	720
Federal									0	(2,589)	1,405
State									0	(857)	708
Total deferred tax (benefit) expense									0	(3,446)	2,113
Income tax expense (benefit)	$ 711	$ 13	$ (52)	$ (40)	$ (224)	$ (209)	$ (3,946)	$ 151	$ 632	$ (4,228)	$ 2,833