Fair Value Measurements and Derivative Instruments (Details 4) In Millions, unless otherwise specified	3 Months Ended			3 Months Ended
	Mar. 31, 2012 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Mar. 31, 2012 Foreign currency forward Not Designated Accumulated other comprehensive income (loss) USD ($)	Mar. 31, 2012 Foreign currency forward Not Designated Accrued expenses and other liabilities USD ($)	Sep. 30, 2012 Cross currency swaps Fixed rate of 5.625% unsecured senior notes USD ($)	Sep. 30, 2012 Cross currency swaps Fixed rate of 5.625% unsecured senior notes EUR (€)	Dec. 31, 2011 Cross currency swaps Fixed rate of 5.625% unsecured senior notes EUR (€)	Sep. 30, 2012 Forward Contracts USD ($)
Gains and losses from derivatives involved in hedging relationships
Deferred gain within accrued expenses and other liabilities					$ 1.7
Net cash proceeds received upon termination of interest swaps						9.1
Deferred loss recognized as increase to depreciation expense over useful life	(9.1)			(10.8)
Deferred loss to be recognized as interest expense over remaining life of debt						(2.6)
Percentage of aggregate cost exposed to fluctuations in the euro exchange rate		15.70%	43.30%
Interest rate on hedged debt (as a percent)						5.625%		5.625%
Unsecured debt							1,000.0
Currency swap agreement, fair value						190.9
Fixed rate on converted debt (as a percent)						6.68%
Notional amount of outstanding foreign exchange contracts		1,900.0	900.0				150.0	150.0
Amount of foreign currency forward contracts not designated as hedging instruments									$ 484.4