Commodity Derivative Instruments Outstanding (Detail) (Current Derivative Contract)	Dec. 31, 2011 gal
Derivatives NOT Designated as Hedging Instruments | Futures Contracts | Refined Products
Derivative [Line Items]
Commodity derivative instruments outstanding	30,324,000	[1]
Derivatives NOT Designated as Hedging Instruments | Physical Fixed Price Derivative Contracts | Refined Products
Derivative [Line Items]
Commodity derivative instruments outstanding	27,744,000	[1]
Derivatives NOT Designated as Hedging Instruments | Physical Index Derivative Contracts
Derivative [Line Items]
Commodity derivative instruments outstanding	155,054,000	[1]
Derivatives Designated as Hedging Instruments | Futures Contracts | Refined Products
Derivative [Line Items]
Commodity derivative instruments outstanding	95,277,000	[1]

[1] Volume represents absolute value of net notional volume position.