Long duration insurance contracts - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Liability for Future Policy Benefit, Activity [Line Items]
Guaranteed minimum death and living benefits associated with variable annuity products liability	$ 1,200	$ 1,250
Reduction in liability for effects of changes in securities markets interest rates and other inputs used to estimate liabilities	65
Long Duration Contracts [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Deferred policy acquisition costs	$ 748		$ 631