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Convertible Securities (Details) (USD $) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2012 item | Dec. 31, 2011
Convertible Securities |  |
Carrying Value | $ 450,100,000 | $ 435,600,000
Carrying Value | 515,500,000 | 512,600,000
Principal amount at maturity | 730,800,000 | 730,800,000
Principal terms of Convertible Debt Securities |  |
Deferred tax liabilities | 24,500,000 |
2008 senior convertible notes |  |
Debt |  |
Number of securities outstanding | 1 |
Convertible Securities |  |
Carrying Value | 450,100,000 | 435,600,000
Principal amount at maturity | 460,000,000 | 460,000,000
Principal terms of Convertible Debt Securities |  |
Denomination | 1,000 |
Current conversion rate | 7.959 |
Current conversion price (in dollars per share) | $ 125.65 |
Stated coupon (as a percent) | 3.95% |
Tax deduction rate (as a percent) | 9.38% |
Junior convertible trust preferred securities |  |
Debt |  |
Number of securities outstanding | 2 |
2007 junior convertible trust preferred securities |  |
Convertible Securities |  |
Carrying Value | 299,400,000 | 297,800,000
Principal amount at maturity | 430,800,000 | 430,800,000
Principal terms of Convertible Debt Securities |  |
Denomination | 50 |
Current conversion rate | 0.250 |
Current conversion price (in dollars per share) | $ 200.00 |
Stated coupon (as a percent) | 5.15% |
Tax deduction rate (as a percent) | 8.00% |
Minimum stock price for convertible notes to be redeemed (in dollars per share) | $ 260 |
2006 junior convertible trust preferred securities |  |
Convertible Securities |  |
Carrying Value | 216,100,000 | 214,800,000
Principal amount at maturity | 300,000,000 | 300,000,000
Principal terms of Convertible Debt Securities |  |
Denomination | $ 50 |
Current conversion rate | 0.333 |
Current conversion price (in dollars per share) | $ 150.00 |
Stated coupon (as a percent) | 5.10% |
Tax deduction rate (as a percent) | 7.50% |
Minimum stock price for convertible notes to be redeemed (in dollars per share) | $ 195 |

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- Definition This element represents the minimum stock price that must be exceeded for the exchangeable notes to be exchanged by debt holders. + References No definition available. + Details
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- Definition Represents the denomination of the principal amount of debt used to determine the number of shares the debt can be converted into at the exchange rate. + References No definition available. + Details
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- Definition Represents the interest rate used to calculate interest expense for tax purposes, as defined by federal income tax regulations. + References No definition available. + Details
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- Definition Represents the deferred taxes generated from the excess of the interest expense calculated under federal income tax regulations over interest expense as calculated for book purposes. + References No definition available. + Details
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- Definition Carrying amount of junior long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months. The debt is convertible, at any time, into a defined number of shares of common stock. Holders of the junior convertible trust preferred securities have no rights to put these securities. + References No definition available. + Details
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- Definition Carrying amount of senior long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months. The debt is convertible into a defined number of shares of common stock upon the occurrence of certain events. The holders may put these securities to the company. + References No definition available. + Details
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- Definition The price per share of the conversion feature embedded in the debt instrument. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number APB14-1 -Paragraph 32 -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 The ratio applied to the debt for purposes of determining the number of shares of the equity security into which the debt will be converted. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Conversion Rate -URI http://asc.fasb.org/extlink&oid=6509012 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 4 -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. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 21 -Paragraph 16, 20 -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 Interest rate stated in the contractual debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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