Business segment data - Reconciliations of Revenues and Earnings (loss) before income taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 371,433	$ 364,482	$ 302,020
Investment gains (losses)	52,799	74,855	(67,899)
Interest expense, not allocated to segments	(5,200)	(5,003)	(4,352)
Non-controlled businesses	1,841	1,973	1,863
Earnings (loss) before income taxes	110,376	120,166	(30,500)
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Revenues	370,892	364,653	301,884
Interest expense, not allocated to segments	(4,982)	(4,630)	(3,946)
Earnings (loss) before income taxes	53,936	43,637	34,775
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Investment gains (losses)	52,799	74,855	(67,899)
Interest expense, not allocated to segments	(427)	(426)	(420)
Non-controlled businesses	1,841	1,973	1,863
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Revenues	541	(171)	136
Interest expense, not allocated to segments	209	53	14
Earnings (loss) before income taxes from operating businesses	$ 2,227	$ 127	$ 1,181