Equity (Schedule of stock repurchases) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013 2013 Repurchase Program	Mar. 31, 2014 2013 Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares purchased (in shares)	2.2	7.2	0.1	0.3
Average price paid per share (in dollars per share)	$ 78.47	$ 0.00		$ 78.99
Total cash utilized	$ 174	$ 500	$ 10	$ 21