Stockholders' Equity (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended	0 Months Ended	1 Months Ended	3 Months Ended
	Apr. 30, 2011	Mar. 31, 2012	Mar. 31, 2011	Apr. 30, 2011 $ 250 Million Dollar Authorization [Member]	Mar. 31, 2011 $ 250 Million Dollar Authorization [Member]	Apr. 30, 2012 $1 Billion Authorization [Member]	Apr. 30, 2011 $1 Billion Authorization [Member]	Mar. 31, 2012 $1 Billion Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Expiration Date of New Authorization								June 30, 2013
Dividends Payable, Amount Per Share		$ 0.26
Increase from previous dividend declarations, amount per share		$ 0.01
Share repurchase authorization				$ 250			$ 1,000
Share repurchase authorization	In April 2011, the Board of Directors replaced its previously approved share repurchase authorization of up to $250 million with a new authorization for repurchases of up to $1 billion of our common shares exclusive of shares repurchased in connection with employee stock plans, expiring on June 30, 2013
Shares repurchased in open market					0.80			1.15
Value of shares repurchased					53			100
Shares repurchased in open market, average price					$ 63.73			$ 86.95
Remaining authorized amount under new authorization						461
Common shares acquired in connection with employee stock plans, shares		0.6	0.6
Common shares acquired in connection with employee stock plans, amount		$ 51	$ 36