Property, plant and equipment and assets held for lease - Depreciation expense (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 3,799	$ 3,643
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	1,089	1,037
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	2,389	2,298
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 321	$ 308