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Income Taxes - Additional Information (Detail) - USD ($) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Income Tax Disclosure [Abstract] |  |  |  |  |
Federal statutory income tax rate |  |  | 21.00% |  | 35.00%
Income tax benefit related to revaluation of net deferred tax liability |  |  |  |  | $ 242,000,000
Additional tax expense related to provisional estimate of one-time transition tax |  |  | $ 0 |  |
Provision (benefit) for income taxes | $ 29,000,000 | $ (13,000,000) | 37,000,000 | $ (43,000,000) |
Unrecognized tax benefit | $ 92,000,000 |  | $ 92,000,000 |  |

X
- Definition Amount of reasonable estimate for income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act for which accounting for tax effect is incomplete. + References No definition available. + Details
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- Definition Amount of reasonable estimate for income tax expense from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act for which accounting for tax effect is incomplete. + References No definition available. + Details
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324 + Details
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