LONG-TERM DEBT (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended			6 Months Ended
	Jun. 30, 2013 ARLP Debt Arrangements	Jun. 30, 2013 ARLP Debt Arrangements Maximum	Jun. 30, 2013 ARLP Debt Arrangements Minimum	Jun. 30, 2013 ARLP Revolving credit facility
Long-Term Debt
Revolving credit facility				$ 700.0
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	1.15
Actual cash flow to interest expense ratio for trailing twelve months	19.0
Letters of credit outstanding				23.5
Line of credit facility, available for borrowing capacity				$ 534.5
Annual commitment fee percentage, undrawn portion				0.25%