Property, plant and equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 46,298	$ 44,773
Property, plant and equipment, accumulated depreciation	(25,185)	(23,939)
Total property, plant and equipment, net	21,113	20,834
Insurance and Other [Member] | Land, buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,761	14,070
Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	26,690	26,063
Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,847	4,640
Railroad [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	85,124	80,692
Property, plant and equipment, accumulated depreciation	(17,899)	(14,978)
Total property, plant and equipment, net	67,225	65,714
Railroad [Member] | Land, track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	67,350	65,843
Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	16,031	13,822
Railroad [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,743	1,027
Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	131,094	125,537
Property, plant and equipment, accumulated depreciation	(38,051)	(35,721)
Total property, plant and equipment, net	93,043	89,816
Utilities and Energy [Member] | Utility generation, transmission and distribution systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	92,759	90,223
Utilities and Energy [Member] | Interstate natural gas pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,328	17,423
Utilities and Energy [Member] | Independent power plants and other assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,650	13,695
Utilities and Energy [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,357	4,196
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net	$ 160,268	$ 155,530