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	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for future policy benefits at June 30	$ 19,635	$ 20,952
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	2	3
Change in benefits, net	(230)	85
Interest accrual	266	268
Foreign currency effect	83	(109)
Ending balance at original discount rate	11,670	11,508
Effect of changes in discount rate assumptions	(850)	318
Expected future policy benefits at June 30	10,820	11,826
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for future policy benefits at June 30	10,820	11,826
Liability for future policy benefits at June 30, net of reinsurance recoverables	10,820	11,826
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	10	318
Effect of actual from expected results	(411)	248
Change in benefits, net	(1,346)	(1,285)
Interest accrual	852	807
Foreign currency effect	100	(1,645)
Ending balance at original discount rate	62,789	58,576
Effect of changes in discount rate assumptions	(12,741)	(8,191)
Expected future policy benefits at June 30	50,048	50,385
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	18	324
Effect of actual from expected results	(251)	90
Change in premiums, net	(1,222)	(988)
Interest accrual	745	701
Foreign currency effect	83	(1,550)
Ending balance at original discount rate	55,908	51,854
Effect of changes in discount rate assumptions	(11,383)	(7,279)
Expected future net premiums at June 30	44,525	44,575
Liability for future policy benefits at June 30	5,523	5,810
Reinsurance recoverables	(1,549)	(1,650)
Liability for future policy benefits at June 30, net of reinsurance recoverables	$ 3,974	$ 4,160