Net Income Per Common Share (Basic And Diluted Income (Loss) From Continuing Operations Per Common Share) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 144	$ 96	$ 274	$ 199
Less: Income allocated to participating securities	2	1	3	2
Net income attributable to common shares	142	95	271	197
Basic net income per common share	$ 0.73	$ 0.54	$ 1.39	$ 1.12
Diluted net income per common share	$ 0.73	$ 0.53	$ 1.39	$ 1.10
Earnings Per Share, Basic [Member]
Basic average common shares	194	175	195	175
Earnings Per Share, Diluted [Member]
Basic average common shares	194	175	195	175
Net effect of the assumed exercise of warrants	0	3	0	3
Diluted average common shares	194	178	195	178
Net Income [Member]
Net income attributable to common shares	$ 142	$ 95	$ 271	$ 197