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Income Taxes (Detail) $ in Billions | 3 Months Ended
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Mar. 31, 2018 USD ($)
Income Tax Narrative (Textual) |
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) | $ 1.9

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- Definition Amount of reasonable estimate for income tax expense (benefit) from effect of Tax Cuts and Jobs Act of 2017 for which accounting for tax effect is incomplete. + References No definition available. + Details
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