Derivative Financial Instruments (Schedule Of NYMEX Contracts And Butane Price Swap Purchase Agreements) (Details)	9 Months Ended
	Sep. 30, 2011 Boe
NYMEX - Cash Flow Hedges [Member]
Derivative [Line Items]
Barrels of petroleum products designated as cash flow hedges	600,000
Derivative, lower remaining maturity range	October
Derivative, higher remaining maturity range	December 2011
NYMEX - Fair Value Hedges [Member]
Derivative [Line Items]
Barrels of crude oil, designated as fair value hedges	700,000
Derivative, lower remaining maturity range	October 2011
Derivative, higher remaining maturity range	November 2013
NYMEX - Economic Hedges [Member]
Derivative [Line Items]
Barrels of petroleum products, used as economic hedges	2,300,000
Derivative, lower remaining maturity range	October 2011
Derivative, higher remaining maturity range	April 2012
Butane Price Swap Purchase Contracts [Member]
Derivative [Line Items]
Barrels of butane	300,000
Derivative, lower remaining maturity range	October 2011
Derivative, higher remaining maturity range	March 2012