Accumulated other comprehensive income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 649,368
Ending Balance	654,471
Unrealized investment gains (losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	117	$ 190
Other comprehensive income	30	(29)
Ending Balance	147	161
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(7,039)	(5,393)
Other comprehensive income	474	(523)
Ending Balance	(6,565)	(5,916)
Long duration insurance contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	2,015	1,353
Other comprehensive income	28	284
Ending Balance	2,043	1,637
Defined benefit pension plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,148	(97)
Other comprehensive income	(38)	3
Ending Balance	1,110	(94)
Other AOCI transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	175	184
Other comprehensive income	6	(22)
Ending Balance	181	162
Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,584)	(3,763)
Other comprehensive income	500	(287)
Ending Balance	$ (3,084)	$ (4,050)