LONG-TERM DEBT (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended			12 Months Ended		12 Months Ended			12 Months Ended								12 Months Ended		12 Months Ended
	Dec. 31, 2013 ARLP Debt Arrangements	Dec. 31, 2013 ARLP Debt Arrangements Maximum	Dec. 31, 2013 ARLP Debt Arrangements Minimum	Dec. 31, 2012 Credit Agreement	Dec. 31, 2013 Credit Agreement	Dec. 31, 2013 ARLP Revolving credit facility	May 23, 2012 ARLP Revolving credit facility	May 23, 2012 ARLP Term Loan	Dec. 31, 2013 ARLP Term Loan June 2014 through March 2016	Dec. 31, 2013 ARLP Term Loan June 2016 through December 2016	Dec. 31, 2013 ARLP Senior notes	Dec. 31, 2013 ARLP Series A Senior Notes	Jun. 26, 2008 ARLP Series A Senior Notes	Dec. 31, 2013 ARLP Series B Senior Notes	Jun. 26, 2008 ARLP Series B Senior Notes	May 23, 2012 Replaced Revolving Credit Facility	Dec. 31, 2012 Terminated term loan	Dec. 29, 2010 Terminated term loan	Dec. 31, 2013 Other item
Long-Term Debt
Revolving credit facility							$ 700.0									$ 142.5			$ 31.1
Aggregate principal amount								250.0			18.0		205.0		145.0			300.0
Effective interest rate (as a percent)					1.82%
Quarterly Principal Repayment Percentage									2.50%	20.00%
Debt issuance costs				4.3
Write off of deferred debt issuance cost																	1.1
Amount repaid on loan																	300
Number of banks																			2
Interest rate (as a percent)											8.31%	6.28%	6.28%	6.72%	6.72%
ARLP debt arrangements requirements, debt to cash flow ratio		3.0
ARLP debt arrangements requirements, cash flow to interest expense ratio			3.0
ARLP debt arrangements requirements, period over which the ratios are required to be maintained	1 year
Actual debt to cash flow ratio for trailing twelve months	1.24
Actual cash flow to interest expense ratio for trailing twelve months	19.8
Letters of credit outstanding						24.2													30.7
Line of credit facility, available for borrowing capacity						$ 425.8
Annual commitment fee percentage, undrawn portion						0.25%