Property, plant and equipment (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 45,129	$ 44,773
Property, plant and equipment, accumulated depreciation	(24,751)	(23,939)
Total property, plant and equipment, net	20,378	20,834
Insurance and Other [Member] | Land, buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,089	14,070
Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	26,072	26,063
Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,968	4,640
Railroad [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	84,099	80,692
Property, plant and equipment, accumulated depreciation	(17,530)	(14,978)
Total property, plant and equipment, net	66,569	65,714
Railroad [Member] | Land, track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	66,744	65,843
Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	15,989	13,822
Railroad [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,366	1,027
Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	128,188	125,537
Property, plant and equipment, accumulated depreciation	(37,285)	(35,721)
Total property, plant and equipment, net	90,903	89,816
Utilities and Energy [Member] | Utility generation, transmission and distribution systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	90,756	90,223
Utilities and Energy [Member] | Interstate natural gas pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	17,882	17,423
Utilities and Energy [Member] | Independent power plants and other assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,352	13,695
Utilities and Energy [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,198	4,196
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net	$ 157,472	$ 155,530