Goodwill and other intangible assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Balance at beginning of year	$ 57,011	$ 54,523
Acquisitions of businesses	1,236	2,732
Other, including foreign currency translation	17	(244)
Balance at end of period	$ 58,264	$ 57,011