Net (Loss) Earnings - Per Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Numerator
Net (loss) earnings available to common stockholders	$ (6.0)	$ 59.7
Distributed and allocated undistributed net earnings to non-vested restricted stockholders	(0.1)	(0.4)
Distributed and allocated undistributed net (loss) earnings -to common stockholders	(6.1)	59.3
Distributed net earnings-dividends paid to common stockholders	(25.1)	(20.7)
Allocation of undistributed net (loss) earnings to common stockholders	(31.2)	38.6
Denominator (1)
Weighted average number of common shares outstanding-basic	191.9	158.7
Basic net (loss) earnings per common share:
Distributed net earnings to common stockholders	$ 0.13	$ 0.13
Allocated undistributed net earnings to common stockholders	$ (0.16)	$ 0.24
Basic net (loss) earnings per common share:	$ (0.03)	$ 0.37
Numerator
Distributed and allocated undistributed net (loss) earnings to common stockholders	(6.1)	59.3
Add: Allocated undistributed net earnings to non-vested restricted stockholders		0.2
Less: Undistributed net earnings reallocated to non-vested restricted stockholders		(0.2)
Net (loss) earnings available to common stockholders - diluted	$ (6.1)	$ 59.3
Denominator (1) (2)
Weighted average number of common shares outstanding-basic	191.9	158.7
Effect of assumed issuance of Settlement agreement shares		18.0
Effect of non-vested restricted stock and restricted stock units		0.2
Weighted average number of common shares outstanding-diluted (2)	191.9	176.9
Diluted net (loss) earnings per common share	$ (0.03)	$ 0.34