CASH DISTRIBUTIONS (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended					1 Months Ended		1 Months Ended		1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	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, 2011 D	Dec. 31, 2009	Dec. 31, 2011 General Partner	Dec. 31, 2010 General Partner	Dec. 31, 2009 General Partner	Jul. 31, 2009 General Partner $0.81 per common unit	Jul. 02, 2009 General Partner $0.81 per common unit	Jul. 31, 2009 General Partner $0.88 per common unit	Jul. 02, 2009 General Partner $0.88 per common unit	Jul. 31, 2009 General Partner Incentive Distribution Agreement prior to July 1, 2009	Dec. 31, 2011 General Partner Incentive Distribution Agreement prior to July 1, 2009 $0.45 per common unit	Dec. 31, 2011 General Partner Incentive Distribution Agreement prior to July 1, 2009 $0.5275 per common unit	Dec. 31, 2011 General Partner Incentive Distribution Agreement prior to July 1, 2009 $0.69 per common unit	Jul. 31, 2009 General Partner Incentive Distribution, as amended	Dec. 31, 2011 General Partner Incentive Distribution, as amended $0.81 per common unit	Dec. 31, 2011 General Partner Incentive Distribution, as amended $0.88 per common unit
CASH DISTRIBUTIONS
Number of days after the end of each quarter for making cash distribution									45
Quarterly cash distributions (in dollars per unit)									$ 0.77
Cash Distributions
Combined general partner interest and incentive distribution interest percentage of quarterly distributions of Available Cash exceeding target levels, threshold														25.00%		50.00%		50.00%	15.00%	25.00%	50.00%	2.00%	15.00%	25.00%
Target level of quarterly distributions (in dollars per common unit)															$ 0.81		$ 0.88		$ 0.45	$ 0.5275	$ 0.69		$ 0.81	$ 0.88
Cash distributions (in dollars per unit)											$ 3.04	$ 2.94	$ 2.87
Cash distribution	$ 42.0	$ 42.0	$ 35.4	$ 35.4	$ 35.4	$ 34.4	$ 34.4	$ 34.4			$ 154.8	$ 138.7	$ 117.0
Incentive distributions to General Partner										$ 5.3			$ 5.3
Percentage of priority income allocations for incentive distributions											100.00%