NONCONTROLLING INTERESTS - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Increase (Decrease) in Partners' Capital
Balance			$ 1,097,649	$ 994,132
NET INCOME	$ 62,872	$ 81,632	167,434	128,521
Other comprehensive income	252	128	505	256
Settlement of directors deferred compensation			(26)	(447)
Vesting of ARLP Long-Term Incentive Plan			(2,988)	(1,001)
Common unit-based compensation			5,765	6,513
Distributions on ARLP common unit-based compensation			(1,560)	(1,975)
Contributions to consolidated company from affiliate noncontrolling interest			251	1,300
Distributions paid by consolidated company to affiliate noncontrolling interest			(337)
Contribution by limited partner - affiliate			800
Distributions to AHGP Partners			(65,849)	(90,393)
Distributions paid by consolidated partnership to noncontrolling interest			(37,993)	(48,061)
Balance	1,163,651	988,845	1,163,651	988,845
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners' Capital
Balance			(16,550)	(14,875)
Other comprehensive income			263	145
Balance	(16,287)	(14,730)	(16,287)	(14,730)
Noncontrolling Interest
Increase (Decrease) in Partners' Capital
Balance			516,122	441,748
NET INCOME			69,840	52,306
Other comprehensive income			242	111
Settlement of directors deferred compensation				(335)
Vesting of ARLP Long-Term Incentive Plan			(2,988)	(1,001)
Common unit-based compensation			5,845	6,382
Distributions on ARLP common unit-based compensation			(1,560)	(1,975)
Contributions to consolidated company from affiliate noncontrolling interest			251	1,300
Distributions paid by consolidated company to affiliate noncontrolling interest			(337)
Distributions paid by consolidated partnership to noncontrolling interest			(37,993)	(48,061)
Balance	549,422	450,475	549,422	450,475
Limited Partners' Capital
Increase (Decrease) in Partners' Capital
Balance			598,077	567,259
NET INCOME			97,594	76,215
Settlement of directors deferred compensation			(26)	(112)
Common unit-based compensation			(80)	131
Contribution by limited partner - affiliate			800
Distributions to AHGP Partners			(65,849)	(90,393)
Balance	$ 630,516	$ 553,100	$ 630,516	$ 553,100