OIL AND NATURAL GAS OPERATIONS (Unaudited) - Oil and Gas Operations (Details)	12 Months Ended
	Dec. 31, 2017 MMBoe MBbls MMcf	Dec. 31, 2016 MMBoe MBbls MMcf	Dec. 31, 2015 MMBoe MBbls MMcf
Proved Developed and Undeveloped Reserves [Roll Forward]
Proved reserves at beginning of period, total (in mmboe) | MMBoe	316.3	354.7	372.7
Revisions of previous estimates (in mmboe) | MMBoe	39.8	(26.0)	(58.9)
Purchases, total (in mmboe) | MMBoe	0.2	0.1	0.0
Extensions and discoveries, total (in mmboe) | MMBoe	115.5	64.1	132.6
Production, total (in mmboe) | MMBoe	(27.8)	(21.6)	(24.0)
Sales, total (in mmboe) | MMBoe		(55.0)	(67.7)
Proved reserves at end of period, total (in mmboe) | MMBoe	444.0	316.3	354.7
Proved developed reserves at end of period (in mmboe) | MMBoe	253.9	162.1	184.0
Proved undeveloped reserves at end of period (in mmboe) | MMBoe	190.1	154.2	170.7
Oil MBbl
Proved Developed and Undeveloped Reserves [Roll Forward]
Proved reserves at beginning of period (in mbbls and mmcf)	199,575	210,691	181,227
Revisions of previous estimates (in mbbls and mmcf)	7,903	(17,840)	(39,537)
Purchases (in mbbls and mmcf)	179	103	2
Extensions and discoveries (in mbbls and mmcf)	66,304	45,129	83,319
Production (in mbbls and mmcf)	(16,951)	(13,213)	(14,023)
Sales (in mbbls and mmcf)		(25,295)	(297)
Proved reserves at end of period (in mbbls and mmcf)	257,010	199,575	210,691
Proved developed reserves at end of period (in mbbls and mmcf)	143,907	101,202	108,319
Proved undeveloped reserves at end of period (in mbbls and mmcf)	113,103	98,373	102,372
NGL MBbl
Proved Developed and Undeveloped Reserves [Roll Forward]
Proved reserves at beginning of period (in mbbls and mmcf)	58,046	71,713	73,463
Revisions of previous estimates (in mbbls and mmcf)	14,853	(6,800)	(11,979)
Purchases (in mbbls and mmcf)	37	21	1
Extensions and discoveries (in mbbls and mmcf)	23,098	10,480	25,530
Production (in mbbls and mmcf)	(5,255)	(3,892)	(4,065)
Sales (in mbbls and mmcf)		(13,476)	(11,237)
Proved reserves at end of period (in mbbls and mmcf)	90,779	58,046	71,713
Proved developed reserves at end of period (in mbbls and mmcf)	52,882	29,767	36,374
Proved undeveloped reserves at end of period (in mbbls and mmcf)	37,897	28,279	35,339
Natural Gas MMcf
Proved Developed and Undeveloped Reserves [Roll Forward]
Proved reserves at beginning of period (in mbbls and mmcf) | MMcf	352,248	433,904	707,926
Revisions of previous estimates (in mbbls and mmcf) | MMcf	102,107	(7,779)	(44,176)
Purchases (in mbbls and mmcf) | MMcf	201	89	2
Extensions and discoveries (in mbbls and mmcf) | MMcf	156,461	50,780	143,022
Production (in mbbls and mmcf) | MMcf	(33,528)	(27,204)	(35,604)
Sales (in mbbls and mmcf) | MMcf		(97,542)	(337,266)
Proved reserves at end of period (in mbbls and mmcf) | MMcf	577,489	352,248	433,904
Proved developed reserves at end of period (in mbbls and mmcf) | MMcf	342,616	187,117	236,112
Proved undeveloped reserves at end of period (in mbbls and mmcf) | MMcf	234,873	165,131	197,792