Shareholders' Equity and Earnings Per Common Share - Calculation of Basic and Diluted Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Equity [Abstract]
Net income (loss)	$ 271.6	$ (225.5)
Less: Net income (loss) attributable to noncontrolling interest	13.5	(13.5)
Net income (loss) available to common shareholders	$ 258.1	$ (212.0)
Weighted-average common shares outstanding, Basic:
Basic	261,100,000	230,000,000
Weighted-average common shares outstanding, Dilutive Effects:
Dilutive	263,500,000	230,000,000
Net income (loss) per common share
Basic	$ 0.99	$ (0.92)
Dilutive	$ 0.98	$ (0.92)
Restricted Stock Units (RSUs)
Weighted-average common shares outstanding, Dilutive Effects:
Dilutive effects of share-based payments	1,000,000	0
Performance shares (PSU awards)
Weighted-average common shares outstanding, Dilutive Effects:
Dilutive effects of share-based payments	600,000	0
RSUs - Deal incentive awards
Weighted-average common shares outstanding, Dilutive Effects:
Dilutive effects of share-based payments	800,000	0