Property, plant and equipment and assets held for lease - Narrative (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 797	$ 802
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	1,924	1,597
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 296	$ 283