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Other Investments - Investments Measured at NAV as a Practical Expedient (Details) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020
NAV of investments at fair value |  |
Unfunded Commitments | $ 114.1 | $ 122.2
Life of funds (generally up to) | 15 years |
Private equity funds |  |
NAV of investments at fair value |  |
Unfunded Commitments | $ 114.1 | 122.2
Investments in other strategies |  |
NAV of investments at fair value |  |
Unfunded Commitments | 0.0 | 0.0
Fair Value Measured at NAV |  |
NAV of investments at fair value |  |
Fair Value | 323.6 | 243.4
Fair Value Measured at NAV | Controlling Interest |  |
NAV of investments at fair value |  |
Fair Value | 217.7 | 164.4
Fair Value Measured at NAV | Private equity funds |  |
NAV of investments at fair value |  |
Fair Value | 307.0 | 235.4
Fair Value Measured at NAV | Investments in other strategies |  |
NAV of investments at fair value |  |
Fair Value | $ 16.6 | $ 8.0

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- Definition Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123874694&loc=SL6742756-110258 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 35 -Paragraph 54B -URI http://asc.fasb.org/extlink&oid=122636397&loc=SL7495116-110257 + Details
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