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Net Income Per Share (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest expense | $ 8.0 | $ 9.5 | $ 9.3 | $ 13.3 | $ 12.7 | $ 12.3 | $ 12.7 | $ 12.7 | $ 40.1 | $ 50.4 | $ 11.6
Maximum percentage of common stock shares for preferred stock conversion | 19.99% |  |  |  |  |  |  |  | 19.99% |  |
Maximum number of common stock shares for preferred stock conversion | 0.9 |  |  |  |  |  |  |  | 0.9 |  |
Convertible Debt [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Interest expense |  |  |  |  |  |  |  |  | $ 20.3 | $ 19.3 | $ 4.7

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- Definition Amount of the cost of borrowed funds accounted for as interest expense for debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 5 + Details
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- Definition Maximum number of common stock shares for preferred stock conversion under NYSE rules prior to obtaining shareholder approval + References No definition available. + Details
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