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Income Taxes (Narrative) (Detail) - USD ($) $ in Millions |  | 12 Months Ended
--- | --- | ---
Jan. 01, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Non Variable Interest Entities [Line Items] |  |  |  |
Federal statutory rate |  | 35.00% | 35.00% | 35.00%
Valuation Allowance Deferred Tax Asset Change In Amount |  | $ 472 |  |
NOL carryforward |  | 2,800 |  |
Alternative minimum tax credit carryforward - Other assets |  | 30 |  |
Foreign tax credit |  | 62 | $ 7 |
Unrecognized Tax Benefits |  | 0 | 0 |
Valuation allowance on net deferred tax asset |  | $ 770 | 7 |
SubsequentEvent [Member] |  |  |  |
Non Variable Interest Entities [Line Items] |  |  |  |
New federal corporate tax rate | 21.00% |  |  |
Other Liabilities [Member] |  |  |  |
Non Variable Interest Entities [Line Items] |  |  |  |
Non U.S. deferred tax liability |  |  | $ 36 |

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