Property, plant and equipment and assets held for lease - Depreciation expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 1,876	$ 1,786
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	542	493
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	1,175	1,141
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 159	$ 152