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Long-duration insurance contracts - Summary of changes in discounted present values of expected future policy benefits and expected future net premiums (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward] |  |
Balance at December 31 | $ 17,616 | $ 20,213
Annuities [Member] |  |
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward] |  |
Balance at beginning of year | 11,212 | 10,640
Balance at beginning of year at original discount rate | 11,681 | 11,549
Effect of actual from expected experience | 3 | 5
Change in benefits, net | (478) | (470)
Interest accrual | 550 | 537
Foreign currency effect | 1 | 60
Ending balance at original discount rate | 11,757 | 11,681
Effect of changes in discount rate assumptions | (1,481) | (469)
Expected future policy benefits at December 31 | 10,276 | 11,212
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward] |  |
Balance at December 31 | 10,276 | 11,212
Liability for future policy benefits at December 31, net of reinsurance recoverables | 10,276 | 11,212
Life and Health [Member] |  |
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward] |  |
Balance at beginning of year | 52,665 | 52,008
Balance at beginning of year at original discount rate | 65,871 | 63,584
Effect of cash flow assumption changes | (348) | (829)
Effect of actual from expected experience | (12,711) | (352)
Change in benefits, net | 1,991 | 1,616
Interest accrual | 1,234 | 1,787
Foreign currency effect | (867) | 65
Ending balance at original discount rate | 55,170 | 65,871
Effect of changes in discount rate assumptions | (11,386) | (13,206)
Expected future policy benefits at December 31 | 43,784 | 52,665
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward] |  |
Balance at beginning of year | 46,916 | 46,129
Balance at beginning of year at original discount rate | 58,731 | 56,535
Effect of cash flow assumption changes | (416) | (880)
Effect of actual from expected experience | (11,104) | (181)
Change in premiums, net | 1,984 | 1,645
Interest accrual | 1,099 | 1,566
Foreign currency effect | (794) | 46
Ending balance at original discount rate | 49,500 | 58,731
Effect of changes in discount rate assumptions | (10,206) | (11,815)
Expected future net premiums at December 31 | 39,294 | 46,916
Balance at December 31 | 4,490 | 5,749
Reinsurance recoverables | (46) | (1,571)
Liability for future policy benefits at December 31, net of reinsurance recoverables | $ 4,444 | $ 4,178

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