Equity (Schedule of stock repurchases) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares purchased (in shares)	1.1	2.2
Average price paid per share (in dollars per share)	$ 104.31	$ 78.47
Total cash utilized	$ 110	$ 174
2013 Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares purchased (in shares)			0.3	0.1
Average price paid per share (in dollars per share)			$ 78.99
Total cash utilized		$ 164	$ 21	$ 10