Earnings per Share (EPS) (Details) (USD $) In Millions, except Per Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
EPS numerator:
Income from continuing operations, net of income taxes	$ 283.5		$ 237.6		$ 756.1		$ 589.4
Less: Net income attributable to noncontrolling interests	7.4		12.2		17.0		23.2
Income from continuing operations attributable to common stockholders, before allocation of earnings to participating securities	276.1		225.4		739.1		566.2
Less: Earnings allocated to participating securities	(1.6)		(1.7)		(4.2)		(4.1)
Income from continuing operations attributable to common stockholders, after earnings allocated to participating securities	274.5	[1]	223.7	[1]	734.9	[1]	562.1	[1]
Loss from discontinued operations, net of income taxes	(2.0)		(1.3)		(3.7)		(2.2)
Net income attributable to common stockholders, after earnings allocated to participating securities	272.5	[1]	222.4	[1]	731.2	[1]	559.9	[1]
EPS denominator:
Weighted average shares outstanding - basic	269.2		267.1		269.0		266.7
Impact of dilutive securities	1.4		1.5		1.5		1.7
Weighted average shares outstanding - diluted	270.6		268.6		270.5		268.4
Basic EPS attributable to common stockholders:
Income from continuing operations	$ 1.02		$ 0.84		$ 2.73		$ 2.11
Loss from discontinued operations	$ (0.01)		$ 0.00		$ (0.01)		$ (0.01)
Net income	$ 1.01		$ 0.84		$ 2.72		$ 2.10
Diluted EPS attributable to common stockholders:
Income from continuing operations	$ 1.01		$ 0.83		$ 2.72		$ 2.09
Loss from discontinued operations	$ (0.01)		$ 0.00		$ (0.01)		$ (0.01)
Net income	$ 1.00		$ 0.83		$ 2.71		$ 2.08
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	0.2				0.2
Maximum [Member]
Earnings per Share (EPS) (Textuals) [Abstract]
Anti-dilutive shares, in millions			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.