INCOME TAXES - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax expense (benefit) at statutory federal income tax rate	$ 37,585	$ (86,503)	$ (518,258)
State income taxes, net of federal income tax benefit	3,235	925	(15,417)
Impact of state law changes	(12)	(9)	(3,075)
Impact of state deferred tax revaluation on San Juan properties	0	(153)	(1,241)
Change in deferred tax valuation allowance	1,975	2,500	1,305
Impact of sequestration on minimum tax credit refund	4,998	0	0
Impact of corporate rate reduction due to the Tax Cuts and Jobs Act (remeasurement of deferred taxes)	(247,844)	0	0
Other, net	622	3,602	1,681
Total income tax benefit	$ (199,441)	$ (79,638)	$ (535,005)
Effective income tax rate (%)	(185.72%)	32.22%	36.13%