Supplemental cash flow information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for income taxes	$ 28,544	$ 7,765	$ 4,236
Non-cash investing and financing activities:
Liabilities assumed in connection with business acquisitions	22	10,938	24,186
Operating lease liabilities arising from obtaining right-of-use assets	2,007	1,645	1,118
Class B common stock issued in exchange for noncontrolling interests	1,045
Insurance and Other [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	1,362	1,670	1,150
Railroad, Utilities and Energy [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	$ 3,577	$ 3,327	$ 3,195