Long duration insurance contracts - Summary of changes in discounted present values of expected future policy benefits and expected future net premiums (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for future policy benefits at March 31	$ 19,937	$ 24,183
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance at beginning of period	10,640	16,153
Balance at beginning of period at original discount rate	11,549	11,261
Effect of actual from expected results	1	1
Change in benefits, net	(116)	43
Interest accrual	133	135
Foreign currency effect	19	(23)
Ending balance at original discount rate	11,586	11,417
Effect of changes in discount rate assumptions	(412)	2,450
Expected future policy benefits at March 31	11,174	13,867
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for future policy benefits at March 31	11,174	13,867
Liability for future policy benefits at March 31, net of reinsurance recoverables	11,174	13,867
Life and Health [Member]
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance at beginning of period	52,008	63,648
Balance at beginning of period at original discount rate	63,584	60,133
Impact of cash flow assumption changes	(1)	486
Effect of actual from expected results	(519)	90
Change in benefits, net	(747)	(517)
Interest accrual	425	404
Foreign currency effect	47	(167)
Ending balance at original discount rate	62,789	60,429
Effect of changes in discount rate assumptions	(12,169)	(2,386)
Expected future policy benefits at March 31	50,620	58,043
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance at beginning of period	46,129	55,960
Balance at beginning of period at original discount rate	56,535	53,277
Impact of cash flow assumption changes	2	458
Effect of actual from expected results	(413)	22
Change in premiums, net	(660)	(357)
Interest accrual	371	351
Foreign currency effect	47	(184)
Ending balance at original discount rate	55,882	53,567
Effect of changes in discount rate assumptions	(10,895)	(2,316)
Expected future net premiums at March 31	44,987	51,251
Liability for future policy benefits at March 31	5,633	6,792
Reinsurance recoverables	(1,565)	(1,857)
Liability for future policy benefits at March 31, net of reinsurance recoverables	$ 4,068	$ 4,935