Long-duration insurance contracts - Summary of undiscounted and discounted expected future gross premiums to be collected and undiscounted expected future benefits for periodic payment annuities and life and health insurance (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits	$ 31,066	$ 31,156	$ 30,260
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future gross premiums	117,078	109,321	102,768
Discounted expected future gross premiums	66,692	66,460	64,378
Undiscounted expected future benefits	$ 111,630	$ 104,544	$ 98,224