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Recent Accounting Pronouncements (Narrative) (Detail) $ in Millions | 6 Months Ended
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Jun. 30, 2018 USD ($)
ASU 2016-01 [Member] | Financial Liabilities [Member] |
Cumulative effect of prospective application of new accounting principle | $ 162
ASU 2016-01 [Member] | Equity Investments [Member] |
Cumulative effect of prospective application of new accounting principle | 2
ASU 2018-02 [Member] |
Cumulative effect of prospective application of new accounting principle | $ 3

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