Property, plant and equipment and assets held for lease - Narrative (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Insurance and Other [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 397	$ 400
Railroad, Utilities and Energy [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	947	795
Finance and Financial Products [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 148	$ 142