Property, plant and equipment and assets held for lease (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 29,349	$ 27,320
Property, plant and equipment, accumulated depreciation	(13,884)	(13,167)
Total property, plant and equipment, net	15,465	14,153
Insurance and Other [Member] | Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,250	6,600
Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	16,673	16,413
Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	3,812	3,136
Insurance and Other [Member] | Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,614	1,171
Railroad [Member] | Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,031	5,983
Railroad [Member] | Track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	44,902	42,588
Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,866	9,493
Railroad [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,257	1,292
Utilities and Energy [Member] | Utility generation, distribution and transmission system [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	67,044	64,645
Utilities and Energy [Member] | Interstate pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,761	6,660
Utilities and Energy [Member] | Independent power plants and other assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,574	5,035
Utilities and Energy [Member] | Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,160	5,194
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	146,595	140,890
Property, plant and equipment, accumulated depreciation	(28,018)	(25,836)
Total property, plant and equipment, net	118,577	115,054
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and assets held for lease, gross	12,613	11,216
Property, plant and equipment and assets held for lease, accumulated depreciation	(3,322)	(3,179)
Total property, plant and equipment and assets held for lease, net	9,291	8,037
Finance and Financial Products [Member] | Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and assets held for lease, gross	221	227
Finance and Financial Products [Member] | Assets held for lease [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and assets held for lease, gross	11,222	9,810
Finance and Financial Products [Member] | Buildings, machinery and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and assets held for lease, gross	$ 1,170	$ 1,179
Minimum [Member] | Insurance and Other [Member] | Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	2 years
Minimum [Member] | Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Minimum [Member] | Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	2 years
Minimum [Member] | Railroad [Member] | Track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	7 years
Minimum [Member] | Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	6 years
Minimum [Member] | Utilities and Energy [Member] | Utility generation, distribution and transmission system [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Minimum [Member] | Utilities and Energy [Member] | Interstate pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Minimum [Member] | Utilities and Energy [Member] | Independent power plants and other assets [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Minimum [Member] | Finance and Financial Products [Member] | Assets held for lease [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Minimum [Member] | Finance and Financial Products [Member] | Buildings, machinery and other [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Maximum [Member] | Insurance and Other [Member] | Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	40 years
Maximum [Member] | Insurance and Other [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	25 years
Maximum [Member] | Insurance and Other [Member] | Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	18 years
Maximum [Member] | Railroad [Member] | Track structure and other roadway [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	100 years
Maximum [Member] | Railroad [Member] | Locomotives, freight cars and other equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	40 years
Maximum [Member] | Utilities and Energy [Member] | Utility generation, distribution and transmission system [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	80 years
Maximum [Member] | Utilities and Energy [Member] | Interstate pipeline assets [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	80 years
Maximum [Member] | Utilities and Energy [Member] | Independent power plants and other assets [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	30 years
Maximum [Member] | Finance and Financial Products [Member] | Assets held for lease [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	30 years
Maximum [Member] | Finance and Financial Products [Member] | Buildings, machinery and other [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	50 years