Financing arrangements (Details 1) (Interest rate swap [Member], USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2013 3.45% notes due 2020 (3.45% 2020 Notes) [Member]	Dec. 31, 2013 4.10% notes due 2021 (4.10% 2021 Notes) [Member]	Dec. 31, 2013 3.875% notes due 2021 (3.875% 2021 Notes) [Member]	Dec. 31, 2013 3.625% notes due 2022 (3.625% 2022 Notes) [Member]
Debt Instrument [Line Items]
Derivative, description of variable rate basis			LIBOR	LIBOR	LIBOR	LIBOR
Derivative, effective interest rate			1.10%	1.70%	2.00%	1.60%
Notional amount	$ 4,400	$ 3,600	$ 900	$ 1,000	$ 1,750	$ 750