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Equity Method Eligible Investments - Carrying Value and Ownership Percentages (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021 | May 07, 2020 | May 06, 2020 | May 31, 2019
--- | --- | --- | --- | --- | ---
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Other long-term investments | $ 1,488.0 | $ 1,377.8 |  |  |
Kudu |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Other long-term investments | 695.9 | 669.5 |  |  |
MediaAlpha |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Common equity securities, at fair value | 168.6 | 261.6 |  |  |
PassportCard/DavidShield |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Other long-term investments | 135.0 | 120.0 |  |  |
Elementum Holdings, L.P. |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Other long-term investments | 30.0 | 45.0 |  |  |
Other Investment Sector |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Other long-term investments | 84.4 | 109.3 |  |  |
Equity Method Investments |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Other long-term investments | $ 0.0 | $ 17.8 |  |  |
Kudu's Participation Contracts | Minimum |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 4.10% | 3.20% |  |  |
Kudu's Participation Contracts | Maximum |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 30.00% | 32.00% |  |  |
MediaAlpha |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 27.10% | 28.00% |  |  |
PassportCard/DavidShield |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 53.80% | 53.80% | 53.80% | 50.00% |
Elementum Holdings, L.P. |  |  |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 29.70% | 29.70% |  |  | 30.00%

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