INCOME TAXES - Components of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current taxes:
Federal	$ (92,236)	$ (23,277)	$ 3,972
State	532	832	758
Total current	(91,704)	(22,445)	4,730
Taxes deferred:
Federal	(113,412)	(62,205)	(513,187)
State	5,675	5,012	(26,548)
Total deferred	(107,737)	(57,193)	(539,735)
Total income tax benefit	$ (199,441)	$ (79,638)	$ (535,005)