Property, plant and equipment (Detail) - USD ($) $ in Millions		Sep. 30, 2024	Dec. 31, 2023
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 50,006	$ 48,634
Property, plant and equipment, accumulated depreciation		(27,706)	(26,604)
Total property, plant and equipment, net		22,300	22,030
Insurance and Other [Member] | Land, buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		15,519	15,058
Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		28,830	28,010
Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		5,657	5,566
Railroad [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		91,176	89,663
Property, plant and equipment, accumulated depreciation		(20,123)	(19,464)
Total property, plant and equipment, net		71,053	70,199
Railroad [Member] | Land, track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		73,453	71,692
Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		15,778	16,256
Railroad [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		1,945	1,715
Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		154,917	148,148
Property, plant and equipment, accumulated depreciation		(43,794)	(40,731)
Total property, plant and equipment, net		111,123	107,417
Utilities and Energy [Member] | Land, buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	[1]	4,796	4,540
Utilities and Energy [Member] | Machinery, equipment and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	[1]	4,177	3,855
Utilities and Energy [Member] | Utility generation, transmission and distribution systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		99,774	96,195
Utilities and Energy [Member] | Interstate natural gas pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		19,750	19,226
Utilities and Energy [Member] | Independent power plants and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		15,195	14,781
Utilities and Energy [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		11,225	9,551
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net		$ 182,176	$ 177,616

[1] Assets held by Pilot