Changes in Capital Structure (Details) (USD $) In Millions, except Share data	1 Months Ended			9 Months Ended
	Aug. 31, 2011	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Common Stock	Sep. 30, 2011 Treasury Stock
Capital Structure
Payments for Repurchase of Equity	$ 58
Changes in common shares issued and outstanding
Shares Issued, Balance at the beginning of the year				304,006,027
Shares Outstanding, Balance at the beginning of the year				247,197,355
Shares issued from LTIP				168,295
Shares issued under ESPP				120,127	120,127
Capital Allocation Plan repurchases (in shares)				(8,879,574)	(8,879,574)
Shares Issued, Balance at the end of the year				304,174,322
Shares Outstanding, Balance at the end of the year				238,606,203
Changes in treasury shares
Beginning balance, treasury shares		(65,568,119)	(56,808,672)		(56,808,672)
Shares issued under ESPP				120,127	120,127
Capital Allocation Plan repurchases (in shares)				(8,879,574)	(8,879,574)
Ending balance, treasury shares		(65,568,119)	(56,808,672)		(65,568,119)
Common stock, shares authorized		500,000,000	500,000,000