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Net Income Per Share (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
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Jun. 30, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012
Earnings Per Share [Abstract] |  |  |  |
Net interest expense on convertible notes and convertible preferred stock dividends | $ 5.1 | $ 4.8 | $ 10.0 | $ 9.5
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 |

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- Definition Interest expense related to convertible debt instruments which has been recognized for the period, including the contractual interest coupon and amortization of the debt discount, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6036836-161870 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number APB14-1 -Paragraph 33 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + 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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