Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Periodic Payment Annuity [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net Interest Expense	$ 136	$ 133
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	944	1,004
Net Interest Expense	$ 33	$ 54