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Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023
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Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | $ 9,850 | $ 3,867
Estimated Fair Value - 12 Months or More | 7,577 | 9,555
Estimated Fair Value | 17,427 | 13,422
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (119) | (67)
Gross Unrealized Losses - 12 Months or More | (678) | (760)
Gross Unrealized Losses | (797) | (827)
Fixed maturities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 9,473 | 3,565
Estimated Fair Value - 12 Months or More | 7,577 | 9,555
Estimated Fair Value | 17,050 | 13,120
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (118) | (65)
Gross Unrealized Losses - 12 Months or More | (678) | (760)
Gross Unrealized Losses | (796) | (825)
Corporate bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 4,542 | 1,559
Estimated Fair Value - 12 Months or More | 4,006 | 4,959
Estimated Fair Value | 8,548 | 6,518
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (65) | (45)
Gross Unrealized Losses - 12 Months or More | (365) | (419)
Gross Unrealized Losses | (430) | (464)
U.S. government and government agencies |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 3,251 | 1,066
Estimated Fair Value - 12 Months or More | 763 | 941
Estimated Fair Value | 4,014 | 2,007
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (36) | (10)
Gross Unrealized Losses - 12 Months or More | (70) | (76)
Gross Unrealized Losses | (106) | (86)
Non-U.S. government securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 1,131 | 365
Estimated Fair Value - 12 Months or More | 813 | 897
Estimated Fair Value | 1,944 | 1,262
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (12) | (4)
Gross Unrealized Losses - 12 Months or More | (98) | (96)
Gross Unrealized Losses | (110) | (100)
Residential mortgage backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 236 | 221
Estimated Fair Value - 12 Months or More | 547 | 522
Estimated Fair Value | 783 | 743
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (3) | (3)
Gross Unrealized Losses - 12 Months or More | (68) | (63)
Gross Unrealized Losses | (71) | (66)
Asset backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 104 | 234
Estimated Fair Value - 12 Months or More | 494 | 1,112
Estimated Fair Value | 598 | 1,346
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1) | (1)
Gross Unrealized Losses - 12 Months or More | (34) | (54)
Gross Unrealized Losses | (35) | (55)
Commercial mortgage backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 187 | 100
Estimated Fair Value - 12 Months or More | 773 | 909
Estimated Fair Value | 960 | 1,009
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1) | (1)
Gross Unrealized Losses - 12 Months or More | (25) | (33)
Gross Unrealized Losses | (26) | (34)
Municipal bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 22 | 20
Estimated Fair Value - 12 Months or More | 181 | 215
Estimated Fair Value | 203 | 235
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | 0 | (1)
Gross Unrealized Losses - 12 Months or More | (18) | (19)
Gross Unrealized Losses | (18) | (20)
Short-term investments |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 377 | 302
Estimated Fair Value - 12 Months or More | 0 | 0
Estimated Fair Value | 377 | 302
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1) | (2)
Gross Unrealized Losses - 12 Months or More | 0 | 0
Gross Unrealized Losses | $ (1) | $ (2)

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