Debt (Details 2) (USD $) In Millions, unless otherwise specified			6 Months Ended			3 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Accounts receivable securitization program	Jun. 30, 2012 Accounts receivable securitization program	Dec. 31, 2012 Accounts receivable securitization program	Jun. 30, 2013 Series C convertible senior debentures	Dec. 31, 2012 Series C convertible senior debentures
Entity's debt and other obligations
Maximum borrowing capacity			$ 150
Amount outstanding	951.6	1,011.6	150.0		135.0	62.4	90.1
Proceeds from the accounts receivable securitization program			482.2	459.3
Payments in respect of accounts receivable securitization program			467.2	459.3
Line of Credit Facility, Amount Outstanding		107.0
Threshold percentage of stock price trigger						120.00%
Threshold trading days						20 days
Threshold consecutive trading days						30 days
Estimated cash settlement on debt conversions						39.2
Payment of principal and accrued interest						29.7
Trading day, reference period						5 days
Accreted principal balance						$ 62.4