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Equity-Method Eligible Investments - Carrying Values of Equity Method Eligible Investments Recorded within Other Long-Term Investments (Details) - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
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Investments in unconsolidated affiliates |  |
Other long-term investments | $ 1,171.2 | $ 856.3
Equity method eligible private equity securities, at fair value |  |
Investments in unconsolidated affiliates |  |
Other long-term investments | 1,087.0 | 761.7
Other, at fair value |  |
Investments in unconsolidated affiliates |  |
Other long-term investments | $ 84.2 | $ 94.6

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- Definition Amount of long-term investments classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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