Financing arrangements (Debt Repayments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Repayments of debt	$ 3,725	$ 2,400	$ 5,605
Repayments of notes payable			5,600
Term loan due 2018 [Member]
Debt Instrument [Line Items]
Repayments of debt	1,975	$ 2,400
Debt instrument, periodic payment, principal			$ 500
2.30% notes due 2016 (2.30% 2016 Notes) [Member]
Debt Instrument [Line Items]
Repayments of debt	$ 750
Stated contractual interest rate on note	2.30%
2.50% notes due 2016 (2.50% 2016 Notes) [Member]
Debt Instrument [Line Items]
Repayments of debt	$ 1,000
Stated contractual interest rate on note	2.50%