Earnings Per Share (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified					12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011 Stock Awards [Member]	Dec. 31, 2010 Stock Awards [Member]	Dec. 31, 2009 Stock Awards [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]	Dec. 31, 2010 Convertible Debt Securities [Member]	Dec. 31, 2009 Convertible Debt Securities [Member]	Dec. 31, 2011 Equity Unit Purchase Agreements [Member]	Dec. 31, 2010 Equity Unit Purchase Agreements [Member]	Dec. 31, 2009 Equity Unit Purchase Agreements [Member]	Dec. 31, 2011 Stock And Performance Awards [Member]	Dec. 31, 2010 Stock And Performance Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Awards with nonforfeitable rights to dividends/dividend equivalents, participating securities outstanding					2	4	7
Number of anti-dilutive securities										26	89	89	27	23	39
Shares that would have been included in diluted earnings per share calculation										2		69
Weighted average exercise price of options								$ 24.00	$ 32.73	$ 35.33
Awards outstanding	46.8	56.1	65.5	46.2												8.0	4.0