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Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
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Debt Securities, Available-for-sale [Line Items] |  |  |  |
Financing Receivable, Allowance for Credit Loss | $ 75 |  | $ 37 |
Available for Sale at Fair value - Amortized cost | 64,977 |  | 59,663 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 60,467 | [1] | $ 52,901 | [2]
Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 100.00% |  | 100.00% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 5,560 |  | $ 7,319 |
Available for Sale at Fair value - Amortized cost | 64,977 |  | 59,663 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 60,467 |  | 52,901 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1,125 |  | 594 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 75 |  | 37 |
Corporate Debt Securities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Available for Sale at Fair value - Amortized cost | 42,014 |  | 38,963 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 38,755 | [1] | $ 33,969 | [2]
Corporate Debt Securities [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 64.10% |  | 64.20% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 3,751 |  | $ 5,135 |
Available for Sale at Fair value - Amortized cost | 42,014 |  | 38,963 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 38,755 |  | 33,969 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 554 |  | 168 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 62 |  | 27 |
Canadian Provincial Governments [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 3,917 | [1] | $ 3,626 | [2]
Canadian Provincial Governments [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 6.50% |  | 6.90% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 33 |  | $ 66 |
Available for Sale at Fair value - Amortized cost | 3,477 |  | 3,311 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 3,917 |  | 3,626 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 473 |  | 381 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 0 |  | 0 |
Residential Mortgage Backed Securities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 1,079 | [1] | $ 941 | [2]
Residential Mortgage Backed Securities [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 7.30% |  | 7.30% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 239 |  | $ 440 |
Available for Sale at Fair value - Amortized cost | 4,661 |  | 4,324 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 4,429 |  | 3,878 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 19 |  | 4 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 12 |  | 10 |
Asset-backed Securities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 4,429 | [1] | $ 3,878 | [2]
Asset-backed Securities [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 2.90% |  | 3.10% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 202 |  | $ 212 |
Available for Sale at Fair value - Amortized cost | 1,969 |  | 1,835 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 1,773 |  | 1,623 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 7 |  | 0 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 1 |  | 0 |
Commercial Mortgage Backed Securities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 1,773 | [1] | $ 1,623 | [2]
Commercial Mortgage Backed Securities [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 1.80% |  | 1.80% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 102 |  | $ 114 |
Available for Sale at Fair value - Amortized cost | 1,173 |  | 1,054 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 1,079 |  | 941 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 8 |  | 1 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 0 |  | 0 |
US Treasury and Government [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 2,520 | [1] | $ 1,482 | [2]
US Treasury and Government [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 4.20% |  | 2.80% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 214 |  | $ 212 |
Available for Sale at Fair value - Amortized cost | 2,725 |  | 1,690 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 2,520 |  | 1,482 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 9 |  | 4 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 0 |  | 0 |
US States and Political Subdivisions Debt Securities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 1,114 | [1] | $ 1,119 | [2]
US States and Political Subdivisions Debt Securities [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 1.80% |  | 2.10% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 129 |  | $ 173 |
Available for Sale at Fair value - Amortized cost | 1,236 |  | 1,282 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 1,114 |  | 1,119 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 7 |  | 10 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 0 |  | 0 |
Debt Security, Government, Non-US [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 3,749 | [1] | $ 3,704 | [2]
Debt Security, Government, Non-US [Member] | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 6.20% |  | 7.00% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 388 |  | $ 489 |
Available for Sale at Fair value - Amortized cost | 4,092 |  | 4,171 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 3,749 |  | 3,704 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 45 |  | 22 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | 0 |  | 0 |
Japanese Government Debt Securities Member |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | $ 3,131 |  | $ 2,559 |
Japanese Government Debt Securities Member | Fixed Maturities [Member] |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Percentage Of Total Available For Sale Securities | 5.20% |  | 4.80% |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | $ 502 |  | $ 478 |
Available for Sale at Fair value - Amortized cost | 3,630 |  | 3,033 |
Fixed maturity securities available-for-sale at fair value (amortized cost of $64,977 and $59,663; allowance for credit losses of $75 and $37) | 3,131 |  | 2,559 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 3 |  | 4 |
Debt Securities, Available-for-Sale, Allowance for Credit Loss | $ 0 |  | $ 0 |
[1] | Excludes limited partnerships that are measured at estimated fair value using the NAV per share (or its equivalent) as a practical expedient. As of December 31, 2023, the fair value of such investments was $856 million
[2] | Excludes limited partnerships that are measured at estimated fair value using the NAV per share (or its equivalent) as a practical expedient. As of December 31, 2022, the fair value of such investments was $683 million.

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