NONCONTROLLING INTERESTS - Partners' Capital (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 1999
Noncontrolling Interest
Noncontrolling interests	$ 475,858	$ 441,748
ARLP
Noncontrolling Interest
Units owned by parent	31,088,338
Accumulated other comprehensive loss attributable to noncontrolling interests
Noncontrolling Interest
Noncontrolling interests	$ (19,498)	(19,682)
Affiliate (SGP)
Noncontrolling Interest
Noncontrolling interests	$ (303,828)	(303,822)	$ (303,900)
Affiliate (SGP) | ARLP
Noncontrolling Interest
Ownership percentage by noncontrolling owners	0.01%
Affiliate (SGP) | Intermediate Partnership
Noncontrolling Interest
Ownership percentage by noncontrolling owners	0.01%
Non-Affiliates (ARLP's non-affiliate limited partners)
Noncontrolling Interest
Noncontrolling interests	$ 794,062	762,667
Affiliate (Cavalier Minerals)
Noncontrolling Interest
Noncontrolling interests	$ 5,122	$ 2,585