Quarterly report pursuant to Section 13 or 15(d)

Amount and Location in the Income Statement for Derivatives Designed as Cash Flow Hedges (Detail)

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Amount and Location in the Income Statement for Derivatives Designed as Cash Flow Hedges (Detail) (Cash Flow Hedging [Member], USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion) $ (18) $ (67)
Interest Rate Contracts | Interest Expense [Member]
   
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion) 1 (8)
Foreign Exchange Contracts | Interest Expense [Member]
   
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion) (1) (59)
Commodity Contracts | Fuel Expense [Member]
   
Derivative Instruments, Gain (Loss) [Line Items]    
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion) $ (18) $ 0