ASSET RETIREMENT OBLIGATIONS - Changes in Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations as of the beginning of the year, including current portion	$ 225,866	$ 316,409	$ 502,513
Liabilities incurred	2,338	15,933	28,606
Liabilities settled	(19,630)	(72,713)	(55,839)
Divestment of properties	0	(248)	(137,801)
Accretion expense	40,229	25,988	28,411
Revision of estimates	(6,784)	(59,503)	(49,481)
Asset retirement obligations as of the end of the year, including current portion	$ 242,019	$ 225,866	$ 316,409