Accumulated other comprehensive income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 506,199
Other comprehensive income, net	(401)	$ (327)
Ending Balance	508,141
Unrealized appreciation of fixed maturity securities, net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	369	536
Other comprehensive income, net	(186)	(67)
Ending Balance	183	469
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,092)	(3,082)
Other comprehensive income, net	(315)	(297)
Ending Balance	(4,407)	(3,379)
Defined benefit pension plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(347)	(1,645)
Other comprehensive income, net	20	40
Ending Balance	(327)	(1,605)
Other AOCI transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	43	(52)
Other comprehensive income, net	80	(3)
Ending Balance	123	(55)
Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,027)	(4,243)
Ending Balance	$ (4,428)	$ (4,570)