Interest Rate Swaps (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Debt and Credit Arrangements [Abstract]
Notional Amount of Interest Rate Cash Flow Hedge Derivatives	$ 300.0		$ 300.0
Amount reclassified from accumulated other comprehensive loss into earnings, derivatives, before tax	0.5	0	0.9	0
Estimated amount reclassified from accumulated other comprehensive loss into earnings within the next twelve months			$ 1.8