Accumulated other comprehensive income (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 506,199
Other comprehensive income, net	(4,207)	$ (591)
Ending Balance	455,430
Unrealized appreciation of fixed maturity securities, net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	369	536
Other comprehensive income, net	(767)	(126)
Ending Balance	(398)	410
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,092)	(3,082)
Other comprehensive income, net	(3,676)	(619)
Ending Balance	(7,768)	(3,701)
Defined benefit pension plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(347)	(1,645)
Other comprehensive income, net	47	112
Ending Balance	(300)	(1,533)
Other AOCI transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	43	(52)
Other comprehensive income, net	189	42
Ending Balance	232	(10)
Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,027)	(4,243)
Ending Balance	$ (8,234)	$ (4,834)