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Income Taxes - Schedule of Components of Net Deferred Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
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Deferred Tax Assets And Liabilities [Line Items] |  |
Deferred tax assets, Depreciation | $ 104 | $ 74
Deferred tax assets, Employee benefits | 2,742 | 2,668
Deferred tax assets, Loss provisions | 368 | 325
Deferred tax assets, Deferred income/expense | 53 | 45
Deferred tax assets, Tax loss carryforwards | 2,186 | 2,035
Deferred tax assets, Tax credit carryforwards | 508 | 477
Deferred tax assets, Derivatives and hedging activities | 117 | 109
Deferred tax assets, Other | 324 | 315
Deferred tax assets, Gross | 6,402 | 6,048
Deferred tax assets, Valuation allowance | (1,400) | (1,398)
Deferred tax assets, net | 5,002 | 4,650
Deferred tax liabilities, Depreciation | 1,015 | 933
Deferred tax liabilities, Employee benefits | 46 | 51
Deferred tax liabilities, Loss provisions | 17 | 9
Deferred tax liabilities, Deferred income/expense | 203 | 181
Deferred tax liabilities, Tax loss carryforwards |  |
Deferred tax liabilities, Tax credit carryforwards |  |
Deferred tax liabilities, Derivatives and hedging activities | 16 | 43
Deferred tax liabilities, Other | 297 | 288
Deferred tax liabilities, Gross | 1,594 | 1,505
Deferred tax liabilities, Valuation allowance |  |
Deferred tax liabilities, Net | $ 1,594 | $ 1,505

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