Income Taxes - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Expense:
Federal	$ (3,530)	$ 103,993	$ 32,999
State	9,772	10,308	5,442
Current Income Tax Expense (Benefit), Total	6,242	114,301	38,441
Deferred Income Tax (Benefit) Expense:
Federal	(60,547)	(33,470)	35,413
State	1,346	(1,692)	3,557
Deferred Income Tax Expense (Benefit), Total	(59,201)	(35,162)	38,970
INCOME TAXES	$ (52,959)	$ 79,139	$ 77,411