DISTRIBUTIONS OF AVAILABLE CASH (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended												12 Months Ended
	Jan. 29, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012
Distribution Made to Member or Limited Partner
Percentage of available cash distributed														100.00%
Period following quarter end for distribution of available cash														50 days
Quarterly per unit distribution paid		$ 0.7200	$ 0.6975	$ 0.6675	$ 0.6375	$ 0.6100	$ 0.5825	$ 0.5550	$ 0.5275	$ 0.5000	$ 0.4825	$ 0.4650	$ 0.4525
Distributions declared per unit	$ 0.74
Approximate distribution to be paid	$ 44.3
ARLP
Distribution Made to Member or Limited Partner
Units owned by parent		15,544,169												15,544,169
Subsidiaries general partner interest percentage														1.98%
Common units percentage														42.20%
MGP
Distribution Made to Member or Limited Partner
Subsidiaries holding percentage														100.00%
Alliance Coal
Distribution Made to Member or Limited Partner
Subsidiaries holding percentage														0.001%