Quarterly report pursuant to Section 13 or 15(d)

Amount and Location in the Income Statement for Derivatives Designated as Fair Value Hedges (Detail)

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Amount and Location in the Income Statement for Derivatives Designated as Fair Value Hedges (Detail) - Fair Value Hedging - Interest Expense - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Interest rate contracts        
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative Amount of Gain (Loss) Recognized in Income $ (19) $ 2 $ (73) $ (22)
Fixed-Rate Debt        
Derivative Instruments, Gain (Loss) [Line Items]        
Hedged Items Amount of Gain (Loss) Recognized in Income $ 19 $ (2) $ 73 $ 22