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Investments (Distribution Of Securities By Percentage Of Fair Value Below Book Value By More Than 5% For A Continuous Twelve Month Period Or Longer) (Detail) $ in Millions | Mar. 31, 2019 USD ($) security | Dec. 31, 2018 USD ($)
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Fixed-maturity securities held as available-for-sale, amortized cost | $ 3,734 | $ 3,817
Available For Sale Securities | $ 3,776 | $ 3,781
> 5% To 15% [Member] |  |
Held To Maturity Securities [Abstract] |  |
Percentage Of Fair Value Below Book Value Minimum | 5.00% |
Percentage Of Fair Value Below Book Value Maximum | 15.00% |
> 5% To 15% [Member] | Unrealized loss position > 12 months |  |
Available For Sale Securities [Abstract] |  |
Number of available-for-sale securities in unrealized loss position | security | 41 |
Fixed-maturity securities held as available-for-sale, amortized cost | $ 212 |
Available For Sale Securities | $ 195 |
> 15% To 25% [Member] |  |
Held To Maturity Securities [Abstract] |  |
Percentage Of Fair Value Below Book Value Minimum | 15.00% |
Percentage Of Fair Value Below Book Value Maximum | 25.00% |
> 15% To 25% [Member] | Unrealized loss position > 12 months |  |
Available For Sale Securities [Abstract] |  |
Number of available-for-sale securities in unrealized loss position | security | 5 |
Fixed-maturity securities held as available-for-sale, amortized cost | $ 2 |
Available For Sale Securities | $ 2 |
> 25% To 50% [Member] |  |
Held To Maturity Securities [Abstract] |  |
Percentage Of Fair Value Below Book Value Minimum | 25.00% |
Percentage Of Fair Value Below Book Value Maximum | 50.00% |
> 25% To 50% [Member] | Unrealized loss position > 12 months |  |
Available For Sale Securities [Abstract] |  |
Number of available-for-sale securities in unrealized loss position | security | 2 |
Fixed-maturity securities held as available-for-sale, amortized cost | $ 14 |
Available For Sale Securities | $ 10 |
> 50% [Member] |  |
Held To Maturity Securities [Abstract] |  |
Percentage Of Fair Value Below Book Value Minimum | 50.00% |
> 50% [Member] | Unrealized loss position > 12 months |  |
Available For Sale Securities [Abstract] |  |
Number of available-for-sale securities in unrealized loss position | security | 3 |
Fixed-maturity securities held as available-for-sale, amortized cost | $ 71 |
Available For Sale Securities | $ 30 |
Greater Than 5% [Member] | Unrealized loss position > 12 months |  |
Available For Sale Securities [Abstract] |  |
Number of available-for-sale securities in unrealized loss position | security | 51 |
Fixed-maturity securities held as available-for-sale, amortized cost | $ 299 |
Available For Sale Securities | $ 237 |

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- Definition Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
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