Earnings per Share (EPS) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
EPS numerator:
Income from continuing operations, net of income taxes	$ 122.9		$ 291.2		$ 520.4		$ 791.3
Less: Net (loss) income attributable to noncontrolling interests	(1.3)		7.4		7.4		17.0
Income from continuing operations attributable to common stockholders, before allocation of earnings to participating securities	124.2		283.8		513.0		774.3
Earnings from continuing operations allocated to participating securities	0.8		1.6		3.8		4.4
Income from continuing operations attributable to common stockholders, after earnings allocated to participating securities	123.4	[1]	282.2	[1]	509.2	[1]	769.9	[1]
Loss from discontinued operations, net of income taxes	(81.3)		(9.7)		(92.7)		(38.9)
Loss from discontinued operations allocated to participating securities	(0.6)		0		(0.8)		(0.2)
Loss from discontinued operations attributable to common stockholders, after earnings allocated to participating securities	(80.7)	[1]	(9.7)	[1]	(91.9)	[1]	(38.7)	[1]
Net income attributable to common stockholders, after earnings allocated to participating securities	42.7	[1]	272.5	[1]	417.3	[1]	731.2	[1]
EPS denominator:
Weighted average shares outstanding - basic	266.2		269.2		268.5		269.0
Impact of dilutive securities	0.6		1.4		0.7		1.5
Weighted average shares outstanding - diluted	266.8		270.6		269.2		270.5
Basic EPS attributable to common stockholders:
Income from continuing operations	$ 0.46		$ 1.05		$ 1.89		$ 2.86
Loss from discontinued operations	$ (0.30)		$ (0.04)		$ (0.34)		$ (0.14)
Net income	$ 0.16		$ 1.01		$ 1.55		$ 2.72
Diluted EPS attributable to common stockholders:
Income from continuing operations	$ 0.46		$ 1.04		$ 1.89		$ 2.84
Loss from discontinued operations	$ (0.30)		$ (0.04)		$ (0.34)		$ (0.13)
Net income	$ 0.16		$ 1.00		$ 1.55		$ 2.71
Earnings per Share (EPS) (Textuals) [Abstract]
Adjustment for participating securities used to calculate diluted EPS was less than	$ 0.1		$ 0.1		$ 0.1		$ 0.1
Anti-dilutive shares, in millions	0.1		0.1		0.1		0.1

[1] The reallocation adjustment for participating securities to arrive at the numerator used to calculate diluted EPS was less than $0.1 million for the periods presented.