Property, plant and equipment and assets held for lease - Depreciation expense (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 5,520	$ 4,963
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	1,595	1,240
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	3,459	3,276
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 466	$ 447