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Fair Value Measurements - Changes in balances of Level 3 financial assets carried at fair value (Details) - USD ($) $ in Millions |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
May 31, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | $ 865 | $ 3,840 | $ 3,706 | $ 3,841
Total realized/unrealized gains (losses) included in Net income |  | 5 | (13) | 161 | (58)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | (1) | 23 | (23) | 47
Purchases and issuances |  | 98 | 104 | 535 | 569
Sales and settlements |  | (52) | (159) | (496) | (432)
Transfer into Level 3 |  | 10 | 247 | 66 | 598
Transfer out of Level 3 |  | (27) | (237) | (332) | (760)
Sale of annuity business | $ (2,719) |  |  |  |
Financial assets, Ending Balance |  | 898 | 3,805 | 898 | 3,805
Fixed maturities |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 605 | 615 | 538 | 571
Total realized/unrealized gains (losses) included in Net income |  | 0 | 1 | (3) | (5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | (1) | 4 | (2) | 8
Purchases and issuances |  | 77 | 16 | 279 | 109
Sales and settlements |  | (48) | (46) | (145) | (107)
Transfer into Level 3 |  | 10 | 23 | 33 | 105
Transfer out of Level 3 |  | (25) | (39) | (82) | (107)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 618 | 574 | 618 | 574
U.S. government agency |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 0 | 0 | 0 | 0
Total realized/unrealized gains (losses) included in Net income |  | 0 | 0 | 0 | 0
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 0
Purchases and issuances |  | 0 | 0 | 0 | 0
Sales and settlements |  | 0 | 0 | 0 | 0
Transfer into Level 3 |  | 0 | 0 | 0 | 0
Transfer out of Level 3 |  | 0 | 0 | 0 | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 0 | 0 | 0 | 0
State and municipal |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 36 | 41 | 39 | 40
Total realized/unrealized gains (losses) included in Net income |  | 0 | 0 | 0 | 0
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 2
Purchases and issuances |  | 0 | 0 | 0 | 0
Sales and settlements |  | 0 | 0 | (3) | (1)
Transfer into Level 3 |  | 8 | 0 | 8 | 0
Transfer out of Level 3 |  | (2) | 0 | (2) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 42 | 41 | 42 | 41
Residential MBS |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 28 | 42 | 38 | 45
Total realized/unrealized gains (losses) included in Net income |  | (1) | (1) | (4) | 0
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | (1)
Purchases and issuances |  | 0 | 0 | 6 | 0
Sales and settlements |  | (1) | (3) | (2) | (5)
Transfer into Level 3 |  | 0 | 8 | 6 | 9
Transfer out of Level 3 |  | (8) | (1) | (26) | (3)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 18 | 45 | 18 | 45
Commercial MBS |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 0 | 6 | 2 | 6
Total realized/unrealized gains (losses) included in Net income |  | 0 | 0 | 0 | 0
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 0
Purchases and issuances |  | 0 | 0 | 0 | 0
Sales and settlements |  | 0 | 0 | 0 | 0
Transfer into Level 3 |  | 0 | 0 | 0 | 0
Transfer out of Level 3 |  | 0 | (4) | (2) | (4)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 0 | 2 | 0 | 2
Collateralized loan obligations |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 6 | 55 | 16 | 1
Total realized/unrealized gains (losses) included in Net income |  | 0 | 0 | 1 | (1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 1 | 1 | 0 | 4
Purchases and issuances |  | 0 | 0 | 0 | 0
Sales and settlements |  | 0 | 0 | (1) | 0
Transfer into Level 3 |  | 0 | 0 | 0 | 52
Transfer out of Level 3 |  | (6) | 0 | (15) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 1 | 56 | 1 | 56
Other asset-backed securities |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 315 | 293 | 305 | 256
Total realized/unrealized gains (losses) included in Net income |  | 1 | (1) | 1 | (6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | (1) | 2 | 0 | 3
Purchases and issuances |  | 41 | 8 | 131 | 69
Sales and settlements |  | (38) | (15) | (110) | (62)
Transfer into Level 3 |  | 0 | 14 | 14 | 41
Transfer out of Level 3 |  | (9) | (8) | (32) | (8)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 309 | 293 | 309 | 293
Corporate and other |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 220 | 178 | 138 | 223
Total realized/unrealized gains (losses) included in Net income |  | 0 | 3 | (1) | 2
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | (1) | 1 | (2) | 0
Purchases and issuances |  | 36 | 8 | 142 | 40
Sales and settlements |  | (9) | (28) | (29) | (39)
Transfer into Level 3 |  | 2 | 1 | 5 | 3
Transfer out of Level 3 |  | 0 | (26) | (5) | (92)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 248 | 137 | 248 | 137
Equity securities |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 245 | 164 | 176 | 161
Total realized/unrealized gains (losses) included in Net income |  | 7 | (5) | 78 | (22)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 0
Purchases and issuances |  | 20 | 5 | 44 | 16
Sales and settlements |  | (4) | 0 | (23) | 0
Transfer into Level 3 |  | 0 | 0 | 0 | 9
Transfer out of Level 3 |  | 0 | (5) | (7) | (5)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 268 | 159 | 268 | 159
Assets of MIE |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 15 | 17 | 21 | 17
Total realized/unrealized gains (losses) included in Net income |  | (2) | (2) | 1 | (4)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 0
Purchases and issuances |  | 1 | 0 | 3 | 0
Sales and settlements |  | 0 | 0 | 0 | 0
Transfer into Level 3 |  | 0 | 0 | 1 | 2
Transfer out of Level 3 |  | (2) | 0 | (14) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 12 | 15 | 12 | 15
Assets of discontinued annuity operations | Annuity subsidiaries |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  |  | 3,044 | 2,971 | 3,092
Total realized/unrealized gains (losses) included in Net income |  |  | (7) | 85 | (27)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  |  | 19 | (21) | 39
Purchases and issuances |  |  | 83 | 209 | 444
Sales and settlements |  |  | (113) | (328) | (325)
Transfer into Level 3 |  |  | 224 | 32 | 482
Transfer out of Level 3 |  |  | (193) | (229) | (648)
Sale of annuity business | $ (2,719) |  |  |  |
Financial assets, Ending Balance |  | $ 0 | $ 3,057 | $ 0 | $ 3,057

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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
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