Amount and Location in the Income Statement for Derivatives Designated as Fair Value Hedges (Detail) - Fair Value Hedging - Interest Expense [Member] - USD ($) $ in Millions  | 
3 Months Ended | |
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Mar. 31, 2017  | 
Mar. 31, 2016  | 
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| Interest Rate Contracts | ||
| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Amount of Gain (Loss) Recognized in Income | $ (24) | $ 95 | 
| Fixed-Rate Debt and Capital Leases | ||
| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Amount of Gain (Loss) Recognized in Income | $ 24 | $ (95) | 
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- Definition Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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