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Income Taxes - Summary of Income Tax Rate (Parenthetical) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Income Taxes [Line Items] |  |
Provisional net increase (decrease) recognized in income tax expense | $ 11 | $ (23)

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- Definition Income Taxes [Line Items] + References No definition available. + Details
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- Definition Amount of reasonable estimate for income tax expense (benefit) for which accounting for tax effect is incomplete pursuant to Tax Cuts and Jobs Act. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 2A -Subparagraph (SAB Topic 5.EE.Q2(b)) -URI http://asc.fasb.org/extlink&oid=116825942&loc=SL116722634-122817 + Details
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