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Incentive Plans (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Incentive Plans (Textual) [Abstract]
Vesting period of Grants in years	4 years
Partnership's historical distribution rate	6.78%
Partnership's historical forfeiture rate	2.51%
Expenses related to Incentive Plan to be reimbursed to general partner	$ 1.5	$ 4.3
Payments made in connection with Long-Term Incentive Plan	6.5	5.7
Unaccrued cost associated with outstanding grants and related DERs	$ 16.5
Market value of common units under the incentive plan	Average closing price over the last 20 trading days prior to the vesting date
Maximum [Member]
Unit Based Compensation Arrangement [Line Items]
Risk free interest rate	0.76%
Volatility rate	47.46%
Minimum [Member]
Unit Based Compensation Arrangement [Line Items]
Risk free interest rate	0.23%
Volatility rate	35.13%