Income Taxes - Components of Tax Expense (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
Current
Federal									$ 80	$ 542	$ 253
State									296	364	183
Total current									376	906	436
Deferred
Federal									38,303	(93,383)
State									1,589	(17,044)
Total deferred									39,892	(110,427)
Total income tax expense	$ (38,589)	$ 872	$ (822)	$ (1,729)	$ (438)	$ (38)	$ 110,065	$ (68)	$ 40,268	$ (109,521)	$ 436