Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums		$ 582	$ 655
Net Interest Expense	$ 537	535	528
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,627	3,760	3,906
Net Interest Expense	$ 221	$ 210	$ 226