Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Differences in the expected income tax provision based on statutory rates applied to earnings before income taxes and the income tax provision reflected in the consolidated statements of operations
Income tax provision	$ 206.8	$ 158.8
Pre-tax income	$ 640.8	$ 482.9
Differences in the expected income tax provision based on statutory rates applied to earnings before income taxes and the income tax provision reflected in the consolidated statements of operations (as a percent)
Effective income tax rate (as a percent)	32.30%	32.90%
Effective tax rate based on pre-tax income exclusive of earnings attributable to noncontrolling interests (as a percent)	35.80%	36.70%