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Investments - Holding gains (losses) on equity securities still held (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Holding Gains (Losses) on Equity Securities Still Held [Line Items] |  |  |  |
Realized gains (losses) on securities still owned | $ 34 | $ (12) | $ (28) | $ (1)
Included in net investment income | 533 | 475 | 1,568 | 1,379
Equity securities |  |  |  |
Holding Gains (Losses) on Equity Securities Still Held [Line Items] |  |  |  |
Realized gains (losses) on securities still owned | 33 | $ (10) | (39) | $ (20)
Equity securities still owned | Equity securities | Accounting Standards Update 2016-01 |  |  |  |
Holding Gains (Losses) on Equity Securities Still Held [Line Items] |  |  |  |
Net holding gains (losses) on equity securities | 27 |  | (35) |
Equity securities still owned | Realized gains (losses) on securities | Equity securities | Accounting Standards Update 2016-01 |  |  |  |
Holding Gains (Losses) on Equity Securities Still Held [Line Items] |  |  |  |
Realized gains (losses) on securities still owned | 25 |  | (51) |
Equity securities still owned | Investment income | Equity securities | Accounting Standards Update 2016-01 |  |  |  |
Holding Gains (Losses) on Equity Securities Still Held [Line Items] |  |  |  |
Included in net investment income | $ 2 |  | $ 16 |

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- Definition Net holding gains (losses) on equity securities in net earnings on securities that were still owned. All equity securities other than those accounted for under the equity method are carried at fair value through net earnings. + References No definition available. + Details
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- Definition Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.2) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263 + Details
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- Definition Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
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