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Recent Accounting Pronouncements (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended |
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Dec. 31, 2018 | Jan. 01, 2019
SubsequentEvent [Member] |  |
Operating lease right of use |  | $ 23
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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- Definition Amount of lessee's right to use underlying asset under operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977 + Details
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