Financial Assets and Liabilities, Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ (97,014)	$ (11,759)
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	630	(12,729)
Fair Value, Measurements, Recurring | Level 1 | Futures Contracts | Refined Products
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	630	112
Financial liabilities		(12,635)
Fair Value, Measurements, Recurring | Level 1 | Futures Contracts | Natural gas
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities		(206)
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	(97,644)	970
Fair Value, Measurements, Recurring | Level 2 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets		3,892
Financial liabilities	(101,911)	(544)
Fair Value, Measurements, Recurring | Level 2 | Physical Fixed Price Derivative Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	5,292	1,522
Financial liabilities	(1,245)	(3,900)
Fair Value, Measurements, Recurring | Level 2 | Physical Index Derivative Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	834
Financial liabilities	$ (614)