NONCONTROLLING INTERESTS - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Increase (Decrease) in Partners' Capital
Balance			$ 994,132	$ 1,018,274
Net income	$ 81,632	$ 94,257	128,521	200,191
Other comprehensive income			256	1,452
Settlement of directors deferred compensation			(447)	(177)
Vesting of ARLP Long-Term Incentive Plan			(1,001)	(2,719)
Common unit-based compensation			6,513	6,121
Distributions on ARLP common unit-based compensation			(1,975)	(1,363)
Contributions to consolidated company from affiliate noncontrolling interest			1,300	1,147
Distributions to AHGP Partners			(90,393)	(110,897)
Distributions paid by consolidated partnership to noncontrolling interest			(48,061)	(56,520)
Balance	988,845	1,055,509	988,845	1,055,509
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners' Capital
Balance			(14,875)	(15,456)
Other comprehensive income			145	650
Balance	(14,730)	(14,806)	(14,730)	(14,806)
Noncontrolling Interest
Increase (Decrease) in Partners' Capital
Balance			441,748	453,496
Net income			52,306	73,711
Other comprehensive income			111	802
Settlement of directors deferred compensation			(335)
Vesting of ARLP Long-Term Incentive Plan			(1,001)	(2,719)
Common unit-based compensation			6,382	6,008
Distributions on ARLP common unit-based compensation			(1,975)	(1,363)
Contributions to consolidated company from affiliate noncontrolling interest			1,300	1,147
Distributions paid by consolidated partnership to noncontrolling interest			(48,061)	(56,520)
Balance	450,475	474,562	450,475	474,562
Limited Partners' Capital
Increase (Decrease) in Partners' Capital
Balance			567,259	580,234
Net income			76,215	126,480
Settlement of directors deferred compensation			(112)	(177)
Common unit-based compensation			131	113
Distributions to AHGP Partners			(90,393)	(110,897)
Balance	$ 553,100	$ 595,753	$ 553,100	$ 595,753