Gains and Losses for Derivative Instruments Not Designated as Hedging Instruments (Detail) (Nondesignated, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ 5,354	$ 26,638
Commodity Derivative Contracts | Crude Oil and Product Purchases
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	5,659	(7,577)
Foreign Exchange Derivative Contracts | Interest and other income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ (305)	$ 34,215