Property, plant and equipment and assets held for lease - Depreciation expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 1,786	$ 1,617
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	493	404
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	1,141	1,066
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 152	$ 147