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Income Taxes (Narrative) (Detail) - USD ($) $ in Millions | Jan. 01, 2018 | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Non Variable Interest Entities [Line Items] |  |  |
NOL carryforward |  | $ 2,700 |
Alternative minimum tax credit carryforward - Other assets |  | 24 |
Foreign tax credit |  | 62 |
Unrecognized Tax Benefits |  | $ 0 | $ 0
New federal corporate tax rate | 21.00% |  |

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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign tax credit carryforwards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319 + Details
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