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Fair Value Measurements (Details 4) (USD $) In Millions, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2013 | Dec. 31, 2012
NAV of investments at fair value |  |
Fair Value | $ 200.7 | $ 187.8
Unfunded Commitments | 73.3 | 75.4
Fair market value of senior notes | 358.9 | 351.8
Fair market value of 2008 senior convertible notes | 572.1 | 510.6
Fair market value of junior convertible trust preferred securities | 810.9 | 719.9
Private equity fund-of-funds |  |
NAV of investments at fair value |  |
Fair Value | 121.9 | 118.9
Unfunded Commitments | 73.3 | 75.4
Liquidation of underlying assets over the life of the funds | 15 years |
Other funds |  |
NAV of investments at fair value |  |
Fair Value | $ 78.8 | $ 68.9

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- Definition Represents the fair value of convertible trust preferred securities. + References No definition available. + Details
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- Definition Represents the fair value of 2008 senior convertible notes. + References No definition available. + Details
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- Definition Represents the fair value of 2042 senior notes. + References No definition available. + Details
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- Definition This element represents the total fair market value of investments in certain entities that calculate net asset value per share (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments). This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements, but may also be used in both the balance sheet and disclosure in the same submission. This item represents alternative investments as of the balance sheet date which may include investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds, and any other investment in which investee management calculates net asset value per share as the primary metric for investment value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=SL6742756-110258 + Details
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- Definition Estimate remaining period the underlying assets are expected to be liquidated by the investees for investments for which net asset value per share is calculated (including by unit, membership interest, or other ownership interest unit measure), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7578670&loc=SL6742756-110258 + Details
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- Definition The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7578670&loc=SL6742756-110258 + Details
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