Summary Of Significant Accounting Policies (Earnings Per Common Share) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Abstract]
Net income for common stock	$ 1,051	$ 992	$ 868
Weighted average common shares outstanding - Basic	292.6	284.3	275.2
Add: Incremental shares attributable to effect of potentially dilutive securities	1.8	1.6	1.1
Adjusted weighted average common shares outstanding - Diluted	294.4	285.9	276.3
Net income for common stock per common share - basic	$ 3.59	$ 3.49	$ 3.16
Net income for common stock per common share - diluted	$ 3.57	$ 3.47	$ 3.14