SEGMENT INFORMATION - EBITDA Reconciliation (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of consolidated Segment Adjusted EBITDA to net income
Consolidated Segment Adjusted EBITDA	[1],[2]			$ 814,243	$ 875,847	$ 749,214
General and administrative				(69,076)	(76,699)	(65,231)
Depreciation, depletion and amortization				(333,713)	(274,566)	(264,911)
Asset impairment charge		$ (89,400)	$ (10,700)	(100,130)
Interest expense, net				(29,693)	(31,913)	(26,081)
Acquisition gain, net		$ 22,500		22,548
Income tax expense				(21)		(1,397)
NET INCOME				$ 304,158	$ 492,669	$ 391,594

[1] Includes equity in income (loss) of affiliates for the years ended December 31, 2015, 2014 and 2013 of $(48.5) million, $(16.6) million and $(25.3) million, respectively, for the Illinois Basin segment and $(0.5) million, $(3) thousand and $0.9 million, respectively, for Other and Corporate.

[2] Segment Adjusted EBITDA is defined as net income (prior to the allocation of noncontrolling interest) before net interest expense, income taxes, depreciation, depletion and amortization, asset impairment charge, acquisition gain, net and general and administrative expenses. Management therefore is able to focus solely on the evaluation of segment operating profitability as it relates to the ARLP Partnership’s revenues and operating expenses, which are primarily controlled by our segments.