NONCONTROLLING INTERESTS - Partners' Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Jun. 16, 2014	Dec. 31, 1999
Noncontrolling Interest
Noncontrolling interests	$ 441,748	$ 453,496
ARLP
Noncontrolling Interest
Units owned by parent	31,088,338		31,088,338
Accumulated Other Comprehensive Loss Attributable To Noncontrolling Interests
Noncontrolling Interest
Noncontrolling interests	$ (19,681)	(20,391)
SGP
Noncontrolling Interest
Noncontrolling interests	$ (303,822)	(303,788)		$ (303,900)
SGP | ARLP
Noncontrolling Interest
Ownership percentage by noncontrolling owners	0.01%
SGP | Intermediate Partnership
Noncontrolling Interest
Ownership percentage by noncontrolling owners	0.01%
Non-Affiliates (ARLP'S Non-Affiliate Limited Partners)
Noncontrolling Interest
Noncontrolling interests	$ 762,666	777,210
Affiliate (Cavalier Minerals)
Noncontrolling Interest
Noncontrolling interests	$ 2,585	$ 465