Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net Interest Expense	$ 550	$ 537
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,830	3,627
Net Interest Expense	$ 135	$ 221