Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums		$ 337
Net Interest Expense	$ 266	268
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,644	1,793
Net Interest Expense	$ 107	$ 106