Summary Of Significant Accounting Policies (Earnings Per Common Share) (Details) (USD $) In Millions, except Per Share data	3 Months Ended						9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Sep. 30, 2011	Sep. 30, 2010
Summary Of Significant Accounting Policies [Abstract]
Net income for common stock	$ 383	$ 165	$ 311	$ 350	$ 183	$ 226	$ 860	$ 759
Weighted average common shares outstanding - Basic	292.9			283.0			292.5	282.2
Add: Incremental shares attributable to effect of potentially dilutive securities	1.7			1.6			1.7	1.5
Adjusted weighted average common shares outstanding - Diluted	294.6			284.6			294.2	283.7
Net income for common stock per common share - basic	$ 1.31			$ 1.24			$ 2.94	$ 2.69
Net income for common stock per common share - diluted	$ 1.30			$ 1.23			$ 2.92	$ 2.68