Accumulated other comprehensive income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 561,273
Ending Balance	571,490
Unrealized gains (losses) on investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	190	$ (187)
Other comprehensive income	(29)	194
Ending Balance	161	7
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,393)	(6,142)
Other comprehensive income	(523)	244
Ending Balance	(5,916)	(5,898)
Long duration insurance contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,353	1,541
Other comprehensive income	284	(291)
Ending Balance	1,637	1,250
Defined benefit pension plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(97)	(552)
Other comprehensive income	3	44
Ending Balance	(94)	(508)
Other AOCI transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	184	288
Other comprehensive income	(22)	(115)
Ending Balance	162	173
Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,763)	(5,052)
Other comprehensive income	(287)	76
Ending Balance	$ (4,050)	$ (4,976)