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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 | 6 Months Ended
--- | --- | --- | ---
May 31, 2021 | Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | $ 3,649 | $ 3,513 | $ 3,706 | $ 3,841
Total realized/unrealized gains (losses) included in Net income |  | 30 | (2) | 156 | (45)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 22 | 72 | (22) | 24
Purchases and issuances |  | 86 | 263 | 437 | 465
Sales and settlements |  | (196) | (50) | (444) | (273)
Transfer into Level 3 |  | 5 | 156 | 56 | 351
Transfer out of Level 3 |  | (12) | (112) | (305) | (523)
Sale of annuity business | $ (2,719) |  |  |  |
Financial assets, Ending Balance |  | 865 | 3,840 | 865 | 3,840
Fixed maturities |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 602 | 545 | 538 | 571
Total realized/unrealized gains (losses) included in Net income |  | (2) | 0 | (3) | (6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 1 | 8 | (1) | 4
Purchases and issuances |  | 60 | 47 | 202 | 93
Sales and settlements |  | (55) | (12) | (97) | (61)
Transfer into Level 3 |  | 4 | 29 | 23 | 82
Transfer out of Level 3 |  | (5) | (2) | (57) | (68)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 605 | 615 | 605 | 615
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 |  | 39 | 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 | 1 | 0 | 2
Purchases and issuances |  | 0 | 0 | 0 | 0
Sales and settlements |  | (3) | (1) | (3) | (1)
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 |  | 36 | 41 | 36 | 41
Residential MBS |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 27 | 44 | 38 | 45
Total realized/unrealized gains (losses) included in Net income |  | 0 | 0 | (3) | 1
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 1 | 0 | (1)
Purchases and issuances |  | 0 | 0 | 6 | 0
Sales and settlements |  | (1) | (1) | (1) | (2)
Transfer into Level 3 |  | 3 | 0 | 6 | 1
Transfer out of Level 3 |  | (1) | (2) | (18) | (2)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 28 | 42 | 28 | 42
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 | 0 | (2) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 0 | 6 | 0 | 6
Collateralized loan obligations |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 6 | 44 | 16 | 1
Total realized/unrealized gains (losses) included in Net income |  | 0 | (1) | 1 | (1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 3 | (1) | 3
Purchases and issuances |  | 0 | 0 | 0 | 0
Sales and settlements |  | 0 | 0 | (1) | 0
Transfer into Level 3 |  | 0 | 9 | 0 | 52
Transfer out of Level 3 |  | 0 | 0 | (9) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 6 | 55 | 6 | 55
Other asset-backed securities |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 326 | 238 | 305 | 256
Total realized/unrealized gains (losses) included in Net income |  | 0 | 1 | 0 | (5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 1 | 1 | 1 | 1
Purchases and issuances |  | 38 | 39 | 90 | 61
Sales and settlements |  | (49) | (6) | (72) | (47)
Transfer into Level 3 |  | 0 | 20 | 14 | 27
Transfer out of Level 3 |  | (1) | 0 | (23) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 315 | 293 | 315 | 293
Corporate and other |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 204 | 172 | 138 | 223
Total realized/unrealized gains (losses) included in Net income |  | (2) | 0 | (1) | (1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 2 | (1) | (1)
Purchases and issuances |  | 22 | 8 | 106 | 32
Sales and settlements |  | (2) | (4) | (20) | (11)
Transfer into Level 3 |  | 1 | 0 | 3 | 2
Transfer out of Level 3 |  | (3) | 0 | (5) | (66)
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 220 | 178 | 220 | 178
Equity securities |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 227 | 155 | 176 | 161
Total realized/unrealized gains (losses) included in Net income |  | 18 | 1 | 71 | (17)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 0
Purchases and issuances |  | 12 | 8 | 24 | 11
Sales and settlements |  | (5) | 0 | (19) | 0
Transfer into Level 3 |  | 0 | 0 | 0 | 9
Transfer out of Level 3 |  | (7) | 0 | (7) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 245 | 164 | 245 | 164
Assets of MIE |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 14 | 16 | 21 | 17
Total realized/unrealized gains (losses) included in Net income |  | (1) | (1) | 3 | (2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 0 | 0 | 0 | 0
Purchases and issuances |  | 1 | 0 | 2 | 0
Sales and settlements |  | 0 | 0 | 0 | 0
Transfer into Level 3 |  | 1 | 2 | 1 | 2
Transfer out of Level 3 |  | 0 | 0 | (12) | 0
Sale of annuity business | 0 |  |  |  |
Financial assets, Ending Balance |  | 15 | 17 | 15 | 17
Assets of discontinued annuity operations | Annuity subsidiaries |  |  |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |  |  |
Financial assets, Beginning Balance |  | 2,806 | 2,797 | 2,971 | 3,092
Total realized/unrealized gains (losses) included in Net income |  | 15 | (2) | 85 | (20)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) |  | 21 | 64 | (21) | 20
Purchases and issuances |  | 13 | 208 | 209 | 361
Sales and settlements |  | (136) | (38) | (328) | (212)
Transfer into Level 3 |  | 0 | 125 | 32 | 258
Transfer out of Level 3 |  | 0 | (110) | (229) | (455)
Sale of annuity business | $ (2,719) |  |  |  |
Financial assets, Ending Balance |  | $ 0 | $ 3,044 | $ 0 | $ 3,044

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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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