Property, plant and equipment (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 46,916	$ 46,298
Property, plant and equipment, accumulated depreciation	(25,708)	(25,185)
Total property, plant and equipment, net	21,208	21,113
Insurance and Other [Member] | Land, buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,533	14,761
Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,190	26,690
Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,193	4,847
Railroad [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	85,637	85,124
Property, plant and equipment, accumulated depreciation	(18,334)	(17,899)
Total property, plant and equipment, net	67,303	67,225
Railroad [Member] | Land, track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	67,861	67,350
Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	16,003	16,031
Railroad [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,773	1,743
Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	140,676	131,094
Property, plant and equipment, accumulated depreciation	(39,006)	(38,051)
Total property, plant and equipment, net	101,670	93,043
Utilities and Energy [Member] | Utility generation, transmission and distribution systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	93,123	92,759
Utilities and Energy [Member] | Interstate natural gas pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,492	18,328
Utilities and Energy [Member] | Independent power plants and other assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,610	14,650
Utilities and Energy [Member] | Land, buildings, improvements and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,205
Utilities and Energy [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,246	5,357
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net	$ 168,973	$ 160,268