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Market risk benefits (MRB Roll-Forward) (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jan. 01, 2021 | Dec. 31, 2023 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Market Risk Benefit [Line Items] |  |  |  |  |  |
Market Risk Benefit, Liability, beginning of period |  |  |  | $ 800 |  |
Market Risk Benefit, Liability, end of period |  |  | $ 771 | 771 | $ 800 |
Market risk benefits gains (losses) |  |  |  | $ (307) | $ 80 | $ 91
Minimum |  |  |  |  |  |
Market Risk Benefit [Line Items] |  |  |  |  |  |
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate |  |  | 0.50% | 0.50% | 0.50% | 0.50%
Annuitization rate |  |  |  | 0.00% | 0.00% | 0.00%
Maximum |  |  |  |  |  |
Market Risk Benefit [Line Items] |  |  |  |  |  |
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate |  |  | 30.00% | 30.00% | 30.40% | 31.50%
Annuitization rate |  |  |  | 100.00% | 100.00% | 100.00%
Weighted Average |  |  |  |  |  |
Market Risk Benefit [Line Items] |  |  |  |  |  |
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate | [1] |  | 4.00% | 4.00% | 3.50% | 4.80%
Annuitization rate | [1] |  |  | 4.50% | 4.40% | 3.60%
Variable Annuity [Member] |  |  |  |  |  |
Market Risk Benefit [Line Items] |  |  |  |  |  |
Market Risk Benefit, Liability, end of period |  | $ 1,163 |  |  |  |
Long-Duration Insurance, Other | Variable Annuity [Member] |  |  |  |  |  |
Market Risk Benefit [Line Items] |  |  |  |  |  |
Market Risk Benefit, Liability, beginning of period |  | 1,163 |  | $ 800 | $ 812 | $ 1,163
Balance, beginning of period, before effect of changes in the instrument-specific credit risk |  | $ 1,079 |  | 776 | 755 | 1,079
Interest rate changes |  |  |  | 26 | (568) | (157)
Effect of changes in equity markets |  |  |  | (195) | 513 | (223)
Effect of changes in volatilities |  |  |  | 20 | 27 | (65)
Market Risk Benefit, Increase (Decrease) from Actual Policyholder Behavior Different from Expected |  |  |  | 18 | (13) | 42
Market Risk Benefit, Increase (Decrease) from Future Expected Policyholder Behavior Assumption |  |  |  | 89 | 40 | 24
Effect of timing and all other |  |  |  | 15 | 22 | 55
Balance, end of period, before effect of changes in the instrument-specific credit risk |  |  | $ 749 | 749 | 776 | 755
Effect of changes in the instrument-specific credit risk |  |  | 22 | 22 | 24 | 57
Market Risk Benefit, Liability, end of period |  |  | 771 | $ 771 | $ 800 | $ 812
Market risk benefit, weighted-average age of policyholders (age) |  |  |  | 74 years | 73 years | 72 years
Market Risk Benefit, Net Amount at Risk | [2] |  | 1,872 | $ 1,872 | $ 2,508 | $ 1,759
Market Risk Benefits Other Gains (Losses) |  |  |  | $ (334) | $ 106 | $ (232)
Long-Duration Insurance, Other | Variable Annuity [Member] | Measurement Input, Annuitization Rate [Member] |  |  |  |  |  |
Market Risk Benefit [Line Items] |  |  |  |  |  |
Market Risk Benefit, Increase (Decrease) from Future Expected Policyholder Behavior Assumption |  |  | $ 92 |  |  |
[1] | The weighted-average lapse and annuitization rates are determined by weighting each treaty's rates by the MRB contract's fair value.
[2] | The net amount at risk is defined as the present value of future claim payments assuming policy account values and guaranteed values are fixed at the valuation date, and reinsurance coverage ends at the earlier of the maturity of the underlying variable annuity policy or the reinsurance treaty. No withdrawals, lapses, and mortality improvements are assumed in the projection. GLB-related risks contain conservative mortality and annuitization assumptions.

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- Definition Amount, before tax, of accumulated other comprehensive income (loss) (AOCI) from (increase) decrease in instrument-specific credit risk on contract or contract feature in long-duration contract issued by insurance entity protecting contract holder from other-than-nominal capital market risk and exposing insurance entity to other-than-nominal capital market risk. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29G -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29G Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (h)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 7B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-7B Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 13K -Subparagraph (k) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-13K + Details
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