Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Benefit Plans [Abstract]
Contributions to the defined contribution plan	$ 18.6	$ 17.5	$ 16.3
Senior Managers and Executive Officers [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Liabilities related to deferred compensation plan included in accrued expenses	10.3	9.5
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of overfunded defined benefit plans	2
Plan assets recorded in other non-current assets	$ 2.1	$ 3.9