Net Income Per Common Share (Basic And Diluted Net Income Per Common Share) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 143	$ 143	$ 277	$ 274
Income allocated to participating securities	2	2	4	3
Net income attributable to common shares	$ 141	$ 141	$ 273	$ 271
Basic average common shares	183	194	184	195
Basic net income per common share	$ 0.77	$ 0.73	$ 1.48	$ 1.39
Basic average common shares	183	194	184	195
Net effect of the assumed exercise of stock options	1	0	1	0
Net effect of the assumed exercise of warrants	3	0	2	0
Diluted average common shares	187	194	187	195
Diluted net income per common share	$ 0.76	$ 0.73	$ 1.46	$ 1.39