Earnings per Common Share (Earnings per Share Computation) (Details) (USD $) Share data in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings per Common Share
Net (loss) income attributable to common shareholders	$ (47,800,000)	$ 124,600,000	$ 84,100,000	$ 245,500,000
Less: Income allocated to participating securities		1,400,000	1,700,000	2,800,000
Net (loss) income available to common shareholders	$ (47,800,000)	$ 123,200,000	$ 82,400,000	$ 242,700,000
Weighted average common shares outstanding	86.2	94.4	85.8	94.9
Dilutive common share equivalents primarily from share-based compensation plans		1.2	2.0	1.2
Weighted average common and common equivalent shares outstanding, assuming dilution	86.2	95.6	87.8	96.1
Common share equivalents not included in the computation of diluted weighted average shares outstanding	2.4