NONCONTROLLING INTERESTS - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Partners' Capital
Balance			$ 994,132	$ 1,018,274
Net income	$ 88,844	$ 82,862	217,365	283,053
Other comprehensive income	127	726	383	2,178
Settlement of directors deferred compensation			(499)	(177)
Vesting of ARLP Long-Term Incentive Plan			(1,001)	(2,719)
Common unit-based compensation			10,039	9,317
Distributions on ARLP common unit-based compensation			(2,673)	(1,995)
Contributions to consolidated company from affiliate noncontrolling interest			2,557	1,483
Distributions paid by consolidated company to affiliate noncontrolling interest			(60)
Distributions to AHGP Partners			(123,318)	(168,365)
Distributions paid by consolidated partnership to noncontrolling interest			(67,007)	(85,628)
Balance	1,029,918	1,055,421	1,029,918	1,055,421
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners' Capital
Balance			(14,875)	(15,456)
Other comprehensive income			199	963
Balance	(14,676)	(14,493)	(14,676)	(14,493)
Noncontrolling Interest
Increase (Decrease) in Partners' Capital
Balance			441,748	453,496
Net income			92,643	100,476
Other comprehensive income			184	1,215
Settlement of directors deferred compensation			(335)
Vesting of ARLP Long-Term Incentive Plan			(1,001)	(2,719)
Common unit-based compensation			9,802	9,148
Distributions on ARLP common unit-based compensation			(2,673)	(1,995)
Contributions to consolidated company from affiliate noncontrolling interest			2,557	1,483
Distributions paid by consolidated company to affiliate noncontrolling interest			(60)
Distributions paid by consolidated partnership to noncontrolling interest			(67,007)	(85,628)
Balance	475,858	475,476	475,858	475,476
Limited Partners' Capital
Increase (Decrease) in Partners' Capital
Balance			567,259	580,234
Net income			124,722	182,577
Settlement of directors deferred compensation			(164)	(177)
Common unit-based compensation			237	169
Distributions to AHGP Partners			(123,318)	(168,365)
Balance	$ 568,736	$ 594,438	$ 568,736	$ 594,438