Accumulated other comprehensive income (Detail) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		$ 473,424
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2018-12 [Member]			Accounting Standards Update 2018-12 [Member]
Ending Balance	$ 436,736	561,273	$ 473,424
Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	443,164			$ 443,164
Unrealized gains (losses) on investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	536	(187)	369	536
Other comprehensive income		377	(556)	(167)
Ending Balance		190	(187)	369
Unrealized gains (losses) on investments [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	536			536
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,082)	(6,142)	(4,092)	(3,082)
Other comprehensive income		749	(2,050)	(1,010)
Ending Balance		(5,393)	(6,142)	(4,092)
Foreign currency translation [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,082)			(3,082)
Long duration insurance contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,751)	1,541	(4,096)	(5,751)
Other comprehensive income		(188)	5,637	1,655
Ending Balance		1,353	1,541	(4,096)
Long duration insurance contracts [Member] | Effect of adoption of ASU 2018-12 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,751)			(5,751)
Defined benefit pension plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,645)	(552)	(347)	(1,645)
Other comprehensive income		455	(205)	1,298
Ending Balance		(97)	(552)	(347)
Defined benefit pension plans [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,645)			(1,645)
Other AOCI transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(52)	288	43	(52)
Other comprehensive income		(104)	245	95
Ending Balance		184	288	43
Other AOCI transactions [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(52)			(52)
Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,994)	(5,052)	(8,123)	(9,994)
Other comprehensive income		1,289	3,071	1,871
Ending Balance		$ (3,763)	$ (5,052)	(8,123)
Accumulated other comprehensive income [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,243)			(4,243)
Accumulated other comprehensive income [Member] | Effect of adoption of ASU 2018-12 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (5,751)			$ (5,751)