Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Sep. 30, 2011
Share repurchases
Average price paid per share	$ 0.00		$ 0.00
Total cash utilized	$ 500		$ 0
2011 Repurchase Program [Member]
Share repurchases
Total number of shares purchased	7.2	[1]	0.8	[1]

[1] include shares received as part of our accelerated share repurchase agreements described in more detail below.