Earnings (Loss) Per Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Income from continuing operations
Income from continuing operations, net of tax	$ 97	$ 339
Less: Preferred stock dividends	10	10
Income from continuing operations, net of tax, available to common shareholders	87	329
Add: Dilutive effect of preferred stock dividends		10
Income from continuing operations, net of tax, available to common shareholders and assumed conversion of preferred shares	87	339
Income (loss) from discontinued operations, net of tax	(1)	162
Net income
Net income	96	501
Less: Preferred stock dividends	10	10
Net income available to common shareholders	86	491
Add: Dilutive effect of preferred stock dividends		10
Net income available to common shareholders and assumed conversion of preferred shares	$ 86	$ 501
Shares
Weighted average common shares outstanding, basic	440.7	444.6
Diluted effect of warrants	26.4	41.1
Diluted effect of stock compensation plans	1.9	1.8
Diluted effect of mandatory convertible preferred shares		20.7
Weighted average shares outstanding and dilutive potential common shares	469.0	508.2
Basic
Income from continuing operations, net of tax, available to common shareholders	$ 0.20	$ 0.74
Income (loss) from discontinued operations, net of tax		$ 0.36
Net income available to common shareholders	$ 0.20	$ 1.10
Diluted
Income from continuing operations, net of tax, available to common shareholders	$ 0.19	$ 0.67
Income (loss) from discontinued operations, net of tax	$ (0.01)	$ 0.32
Net income available to common shareholders	$ 0.18	$ 0.99