Share Repurchase Programs (Details) (USD $) In Millions, unless otherwise specified	2 Months Ended	9 Months Ended
	Feb. 29, 2012	Sep. 30, 2012	Sep. 30, 2011
Share Repurchase Program
Amount authorized		$ 4,300
Number of shares repurchased		45.0
Share Repurchase Program July 2008 [Member]
Share Repurchase Program
Share repurchase program periods			July 2008 - October 2008
Amount authorized		400
Number of shares repurchased		5.9
Share Repurchase Program May 2009 [Member]
Share Repurchase Program
Share repurchase program periods			May 2009 - July 2009
Amount authorized		250
Number of shares repurchased		3.7
Share Repurchase Program July 2009 [Member]
Share Repurchase Program
Share repurchase program periods			July 2009 - January 2010
Amount authorized		750
Number of shares repurchased		9.7
Share Repurchase Program Feb 2010 [Member]
Share Repurchase Program
Share repurchase program periods			February 2010 - May 2010
Amount authorized		250
Number of shares repurchased		3.3
Share Repurchase Program Aug 2010 [Member]
Share Repurchase Program
Share repurchase program periods			August 2010 - August 2011
Amount authorized		1,400
Number of shares repurchased		15.0
Share Repurchase Program Aug 2011 [Member]
Share Repurchase Program
Share repurchase program periods			August 2011- February 2012
Amount authorized		750
Number of shares repurchased	1.6	6.7
Share Repurchase Program Aug 2012 [Member]
Share Repurchase Program
Share repurchase program periods		August 2012 -
Amount authorized		$ 500
Number of shares repurchased		0.7