Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Interest Rate Swap [Member]	Mar. 31, 2013 Interest Rate Swap [Member] Cash Flow Hedging [Member]	Mar. 31, 2012 Interest Rate Swap [Member] Cash Flow Hedging [Member]	Mar. 31, 2013 Interest Rate Swap [Member] Cash Flow Hedging [Member] Interest Expense [Member]	Mar. 31, 2012 Interest Rate Swap [Member] Cash Flow Hedging [Member] Interest Expense [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Accrued Expenses And Other Current Liabilities [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Accrued Expenses And Other Current Liabilities [Member] Interest Rate Swap [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Other Non-current Liabilities [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Other Non-current Liabilities [Member] Interest Rate Swap [Member]
Interest Rate Risk [Abstract]
Term of interest rate swap	4 years
LIBOR-based interest rate	LIBOR-based interest rate to 1.25%
Variable interest rate (in hundredths)	1.25%
Senior credit facility balance covered under interest rate swap contracts	$ 250.0
Derivatives, Fair Value [Line Items]
Interest rate swap expiration date		Dec. 30, 2015
Fair value of derivative liability							3.7	4.3	1.7	2.3	2.0	2.0
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) recognized in AOCI on derivative (effective portion)			(0.6)	(0.4)
Amount of gain/(loss) reclassified from AOCI into income (effective portion)					(0.8)	(0.8)
Amount of gain/(loss) recognized in income on derivative (ineffective portion)					$ 0	$ 0