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Derivatives - Gain (loss) included in the Statement of Earnings for changes in the fair value of derivatives that do not qualify for hedge accounting (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Derivative, Gain (Loss) on Derivative, Net [Abstract] |  |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net |  | $ (103) | $ (80) | $ (83)
MBS with embedded derivatives | Realized gains (losses) on securities |  |  |  |
Derivative, Gain (Loss) on Derivative, Net [Abstract] |  |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net |  | (6) | (9) | (16)
Public company warrants | Realized gains (losses) on securities |  |  |  |
Derivative, Gain (Loss) on Derivative, Net [Abstract] |  |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net |  | 0 | 0 | 0
Fixed-indexed annuities (embedded derivative) | Annuity benefits |  |  |  |
Derivative, Gain (Loss) on Derivative, Net [Abstract] |  |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | [1] | (589) | (211) | (17)
Equity index call options | Annuity benefits |  |  |  |
Derivative, Gain (Loss) on Derivative, Net [Abstract] |  |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net |  | 494 | 141 | (56)
Reinsurance contract (embedded derivative) | Net investment income |  |  |  |
Derivative, Gain (Loss) on Derivative, Net [Abstract] |  |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net |  | $ (2) | $ (1) | $ 6
[1] | The change in fair value of the embedded derivative includes losses related to unlocking of actuarial assumptions of $25 million in 2017 compared to $17 million in 2016 and $28 million in 2015.

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + Details
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