WHITE OAK TRANSACTIONS (Details) (USD $)	12 Months Ended		0 Months Ended	3 Months Ended	12 Months Ended		15 Months Ended	0 Months Ended			3 Months Ended	12 Months Ended					0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 22, 2011 White Oak	Dec. 31, 2011 White Oak	Dec. 31, 2012 White Oak	Dec. 31, 2011 White Oak	Dec. 31, 2012 White Oak	Sep. 22, 2011 White Oak Minimum	Sep. 22, 2011 White Oak Maximum	Sep. 22, 2011 White Oak Reserve Acquisition	Dec. 31, 2011 White Oak Reserve Acquisition	Dec. 31, 2012 White Oak Reserve Acquisition T	Dec. 31, 2012 White Oak Reserve Acquisition Forecast	Dec. 31, 2012 White Oak Services Agreement T	Dec. 31, 2012 White Oak Services Agreement Up to Minimum Throughput Quantity	Dec. 31, 2012 White Oak Services Agreement Above Minimum Throughput Quantity	Jun. 18, 2012 White Oak Equipment Financing Commitment	Sep. 22, 2011 White Oak Equipment Financing Commitment
White oak transactions
Amount funded by partnership			$ 69,500,000				$ 121,500,000
Expected funding by partnership								300,500,000	425,500,000
Expected period of funding								2 years	3 years
Coal reserves, rights purchased, approximate tonnage												204,900,000
Coal reserves tonnage developed for future mining												105,200,000
Payment for acquisition of coal reserves and other assets	34,601,000	50,800,000								33,800,000	17,000,000	34,600,000
Commitment for additional coal reserve acquisitions												54,600,000
Minimum monthly royalties receivable													1,625,000
Purchase of equity investment			35,700,000	7,000,000	59,800,000
Remaining equity investment commitment								114,300,000
Equity investment commitment								150,000,000	275,000,000
Additional equity investment commitment									125,000,000
Equity method investment, net					102,500,000		102,500,000
Percentage of distributions which Series A Units are entitled to receive					100.00%
Potential ownership interest (as a percent)								20.00%	40.00%
Percentage of distributions which the partnership is entitled to receive								20.00%
Voting Interest(as a percent)				6.60%	14.60%	6.60%	14.60%
Allocated losses					15,300,000	4,300,000
Throughput fee (in dollars per ton)															5.00	2.40
Minimum throughput quantity of feedstock coal, per month														666,667
Additional commitment for construction loan														10,500,000
Term of construction loan														20 years
Construction Loan utilized														3,000,000
Equipment financing commitment																		100,000,000
Term of equipment financing commitment loan years																		5 years
Repayment of prior advances on equipment financing commitment loan																	2,200,000
Cancellation fee																	$ 2,000,000