Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Periodic Payment Annuity [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net Interest Expense	$ 138	$ 136
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	951	944
Net Interest Expense	$ 33	$ 33