Income Taxes - Components of Federal and State Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current expense
Federal taxes				$ 2,875	$ 1,552	$ 44,779
State taxes				6,434	(630)	10,936
Total current provision				9,309	922	55,715
Deferred expense (benefit)
Federal taxes				6,708	(52,886)	(47,056)
State taxes				(500)	(1,169)	(5,819)
Total deferred provision				6,208	(54,055)	(52,875)
Income tax expense (benefit)	$ 3,531	$ 1,828	$ 5,359	$ 15,517	$ (53,133)	$ 2,840
Effective tax rate				25.00%	(400.80%)	146.00%

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

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