SUPPLEMENTAL INFORMATION ON OIL AND NATURAL GAS OPERATIONS - UNAUDITED - Summary of Estimated Proved Oil and Natural Gas Reserve (Details) MMcf in Thousands, MBbls in Thousands	12 Months Ended
	Dec. 31, 2016 MMcf MBbls	Dec. 31, 2015 MMcf MBbls	Dec. 31, 2014 MMcf MBbls
Oil (MBbls)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance | MBbls	30,276	42,397	43,827
Revisions of previous estimates | MBbls	(751)	(6,818)	(624)
Extensions, discoveries and other additions | MBbls	63	862	9,650
Purchase of producing properties | MBbls		685
Sale of reserves | MBbls		(859)	(4,888)
Production | MBbls	(6,308)	(5,991)	(5,568)
Estimated proved reserves, ending balance | MBbls	23,280	30,276	42,397
Estimated proved developed reserves: | MBbls	18,269	21,734	22,957
Estimated proved undeveloped reserves: | MBbls	5,011	8,542	19,440
NGLs (MBbls)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance | MBbls	6,458	27,817	23,297
Revisions of previous estimates | MBbls	6,352	(20,777)	(331)
Extensions, discoveries and other additions | MBbls	2	11	7,521
Purchase of producing properties | MBbls		1,808
Sale of reserves | MBbls		0	(556)
Production | MBbls	(2,183)	(2,401)	(2,114)
Estimated proved reserves, ending balance | MBbls	10,629	6,458	27,817
Estimated proved developed reserves: | MBbls	9,255	4,784	13,743
Estimated proved undeveloped reserves: | MBbls	1,374	1,674	14,074
Natural Gas (MMcf)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance | MMcf	121,858	493,843	460,766
Revisions of previous estimates | MMcf	24,858	(362,102)	(4,631)
Extensions, discoveries and other additions | MMcf	45	1,499	131,617
Purchase of producing properties | MMcf		26,136
Sale of reserves | MMcf		(1,061)	(46,483)
Production | MMcf	(29,441)	(36,457)	(47,426)
Estimated proved reserves, ending balance | MMcf	117,320	121,858	493,843
Estimated proved developed reserves: | MMcf	90,741	90,262	249,924
Estimated proved undeveloped reserves: | MMcf	26,579	31,596	243,919
Oil, Natural Gas and NGLs (MMcfe)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance | MMcf	342,260	915,124	863,513
Revisions of previous estimates | MMcf	58,465	(527,675)	(10,362)
Extensions, discoveries and other additions | MMcf	435	6,738	234,639
Purchase of producing properties | MMcf		41,095
Sale of reserves | MMcf		(6,213)	(79,151)
Production | MMcf	(80,387)	(86,809)	(93,515)
Estimated proved reserves, ending balance | MMcf	320,773	342,260	915,124
Estimated proved developed reserves: | MMcf	255,884	249,366	470,118
Estimated proved undeveloped reserves: | MMcf	64,889	92,894	445,006