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Fair Value Disclosures (Financial Assets and Liabilities Measured at Fair Value) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets: SERP $ 2.1 $ 1.7
Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets: SERP 0 0
Level 2 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets: SERP 2.1 1.7
Level 3 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Assets: SERP $ 0 $ 0