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Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt and Equity Securities, FV-NI [Line Items] |  |
Equity securities | $ 1,937 | $ 1,814
Common stocks |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Equity securities, at cost | 1,164 | 1,241
Equity securities | 1,283 | 1,148
Equity securities, fair value in excess of cost | 119 | (93)
Perpetual preferred stocks |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Equity securities, at cost | 640 | 705
Equity securities | 654 | 666
Equity securities, fair value in excess of cost | 14 | (39)
Equity securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Equity securities, at cost | 1,804 | 1,946
Equity securities | 1,937 | 1,814
Equity securities, fair value in excess of cost | $ 133 | $ (132)

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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI) in excess of the cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value. + References No definition available. + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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