NONCONTROLLING INTERESTS - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Increase (Decrease) in Partners' Capital
Balance	$ 1,097,649	$ 994,132
NET INCOME	104,562	46,889
Other comprehensive income	253	128
Settlement of directors deferred compensation	(14)	(427)
Vesting of ARLP Long-Term Incentive Plan	(2,988)	(1,001)
Common unit-based compensation	2,781	3,195
Distributions on ARLP common unit-based compensation	(862)	(1,277)
Contributions to consolidated company from affiliate noncontrolling interest	251	796
Distributions paid by consolidated company to affiliate noncontrolling interest	(190)
Contribution by limited partner - affiliate	800
Distributions to AHGP Partners	(32,925)	(57,468)
Distributions paid by consolidated partnership to noncontrolling interest	(18,948)	(29,111)
Balance	1,150,369	955,856
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners' Capital
Balance	(16,550)	(14,875)
Other comprehensive income	155	90
Balance	(16,395)	(14,785)
Noncontrolling Interest
Increase (Decrease) in Partners' Capital
Balance	516,122	441,748
NET INCOME	49,551	16,047
Other comprehensive income	98	38
Settlement of directors deferred compensation		(335)
Vesting of ARLP Long-Term Incentive Plan	(2,988)	(1,001)
Common unit-based compensation	2,884	3,135
Distributions on ARLP common unit-based compensation	(862)	(1,277)
Contributions to consolidated company from affiliate noncontrolling interest	251	796
Distributions paid by consolidated company to affiliate noncontrolling interest	(190)
Distributions paid by consolidated partnership to noncontrolling interest	(18,948)	(29,111)
Balance	545,918	430,040
Limited Partners' Capital
Increase (Decrease) in Partners' Capital
Balance	598,077	567,259
NET INCOME	55,011	30,842
Settlement of directors deferred compensation	(14)	(92)
Common unit-based compensation	(103)	60
Contribution by limited partner - affiliate	800
Distributions to AHGP Partners	(32,925)	(57,468)
Balance	$ 620,846	$ 540,601