Interest Rate Swaps (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Debt and Credit Arrangements [Abstract]
Notional Amount of Interest Rate Cash Flow Hedge Derivatives	$ 300.0
Amount reclassified from accumulated other comprehensive loss into earnings, derivatives, before tax	0.4	0
Estimated amount reclassified from accumulated other comprehensive loss into earnings within the next twelve months	$ 1.8

Before tax amount of the income statement impact of the reclassification adjustment of accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges realized in net income. Also includes reclassification adjustments of an entity's share of an equity investee's deferred hedging gain (loss) realized in net income.

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-Name Statement of Financial Accounting Standard (FAS)

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-Name Accounting Standards Codification

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+ Details