Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Interest Rate Swap [Member]	Jun. 30, 2013 Designated as Hedging Instrument [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member]	Jun. 30, 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]	Jun. 30, 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
Derivatives, Fair Value [Line Items]
Interest rate swap expiration date		Dec. 30, 2015
Fair value of derivative liability			$ 2.7	$ 4.3	$ 1.8	$ 2.3	$ 0.9	$ 2.0