Derivatives (Schedule Of Outstanding Derivatives Entered Into To Hedge Inventory Or Fixed Price Purchase Commitments) (Details) (Not Designated As Hedging Instrument [Member], USD $)	Mar. 31, 2012
Sell (Short) Contracts [Member] | Crude Oil Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	$ 98
Weighted average contract price per bbl	$ 117.61
Sell (Short) Contracts [Member] | Heating Oil Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	113
Weighted average contract price per gal	$ 3.19
Sell (Short) Contracts [Member] | RBOB Gasoline Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	81
Weighted average contract price per gal	$ 3.33
Sell (Short) Contracts [Member] | Fuel Oil Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	275
Weighted average contract price per bbl	$ 108.38
Sell (Short) Contracts [Member] | Crude Oil Options [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	350
Weighted average premium received	$ 1.63
Sell (Short) Contracts [Member] | Heating Oil Options [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	40
Weighted average premium received	$ 0.08
Sell (Short) Contracts [Member] | RBOB Gasoline Options [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	10
Weighted average premium received	$ 0.08
Buy (Long) Contracts [Member] | Crude Oil Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	44
Weighted average contract price per bbl	$ 114.33
Buy (Long) Contracts [Member] | RBOB Gasoline Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	4
Weighted average contract price per gal	$ 3.39
Buy (Long) Contracts [Member] | Crude Oil Options [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls)	$ 100
Weighted average premium received	$ 0.28