Share Repurchases (Details) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012
Disclosure of Repurchase Agreements [Abstract]
Authorized shares repurchase		110	110
Treasury Stock, Shares, Acquired	99	98
Shares outstanding		121	120