Income taxes - Narrative (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Undistributed earnings of foreign subsidiaries for which no deferred income taxes have been established	$ 9,300,000,000
Unrecognized tax benefits	692,000,000	866,000,000
Unrecognized tax benefits that would impact effective tax rate	$ 560,000,000