Supplemental cash flow information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for income taxes	$ 17,466	$ 5,768
Non-cash investing and financing activities:
Liabilities assumed in connection with business acquisitions	20	10,832
Class B common stock issued in exchange for noncontrolling interests	625
Insurance and Other [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	1,047	1,077
Railroad, Utilities and Energy [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	$ 2,761	$ 2,670