Accumulated other comprehensive income (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 561,273
Ending Balance	629,069
Unrealized gains (losses) on investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	190	$ (187)
Other comprehensive income	81	178
Ending Balance	271	(9)
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,393)	(6,142)
Other comprehensive income	78	(187)
Ending Balance	(5,315)	(6,329)
Long duration insurance contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,353	1,541
Other comprehensive income	(10)	786
Ending Balance	1,343	2,327
Defined benefit pension plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(97)	(552)
Other comprehensive income	(44)	51
Ending Balance	(141)	(501)
Other AOCI transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	184	288
Other comprehensive income	(34)	(48)
Ending Balance	150	240
Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,763)	(5,052)
Other comprehensive income	71	780
Ending Balance	$ (3,692)	$ (4,272)