NONCONTROLLING INTERESTS - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Increase (Decrease) in Partners' Capital
Balance			$ 1,097,649	$ 994,132
NET INCOME	$ 60,943	$ 88,844	228,377	217,365
Other comprehensive income	341	127	846	383
Settlement of directors deferred compensation			(26)	(499)
Vesting of ARLP Long-Term Incentive Plan			(2,988)	(1,001)
Exchange Transaction fees			(2,342)
Common unit-based compensation			8,884	10,039
Distributions on ARLP common unit-based compensation			(2,392)	(2,673)
Contributions to consolidated company from affiliate noncontrolling interest			251	2,557
Distributions paid by consolidated company to affiliate noncontrolling interest			(855)	(60)
Contribution by limited partner - affiliate			800
Distributions to AHGP Partners			(109,548)	(123,318)
Distributions paid by consolidated partnership to noncontrolling interest			(59,751)	(67,007)
Balance	1,158,905	1,029,918	1,158,905	1,029,918
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners' Capital
Balance			(16,550)	(14,875)
Other comprehensive income			468	199
Other comprehensive income reclassification resulting from the Exchange Transaction			(9,188)
Balance	(25,270)	(14,676)	(25,270)	(14,676)
Noncontrolling Interest
Increase (Decrease) in Partners' Capital
Balance			516,122	441,748
NET INCOME			91,661	92,643
Other comprehensive income			378	184
Other comprehensive income reclassification resulting from the Exchange Transaction			9,188
Settlement of directors deferred compensation				(335)
Vesting of ARLP Long-Term Incentive Plan			(2,988)	(1,001)
Common unit-based compensation			8,947	9,802
Distributions on ARLP common unit-based compensation			(2,392)	(2,673)
Contributions to consolidated company from affiliate noncontrolling interest			251	2,557
Distributions paid by consolidated company to affiliate noncontrolling interest			(855)	(60)
Distributions paid by consolidated partnership to noncontrolling interest			(59,751)	(67,007)
Balance	560,561	475,858	560,561	475,858
Limited Partners' Capital
Increase (Decrease) in Partners' Capital
Balance			598,077	567,259
NET INCOME			136,716	124,722
Settlement of directors deferred compensation			(26)	(164)
Exchange Transaction fees			(2,342)
Common unit-based compensation			(63)	237
Contribution by limited partner - affiliate			800
Distributions to AHGP Partners			(109,548)	(123,318)
Balance	$ 623,614	$ 568,736	$ 623,614	$ 568,736