Annual report pursuant to Section 13 and 15(d)

Receivables and Allowance for Doubtful Receivables (Narrative) (Details)

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Receivables and Allowance for Doubtful Receivables (Narrative) (Details) (USF Program [Member], USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
USF Program [Member]
     
Accounts Notes And Loans Receivable [Line Items]      
Revenue Support, Percent 19.00% 19.00% 18.00%
Receivables Net Current $ 70.1 $ 69.8