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Equity-Method Eligible Investments - Significant Equity Method Eligible Investments (Details) - USD ($) $ in Millions | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2020 | Dec. 31, 2019 | May 31, 2019 | Feb. 26, 2019 | Feb. 25, 2019
PassportCard/DavidShield |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 53.80% | 50.00% |  |  |
Stock issued during period, value, acquisitions | $ 15 |  |  |  |
MediaAlpha |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 48.30% | 48.30% |  | 48.30% | 61.00%
durchblicker |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 45.00% | 45.00% |  |  |
Elementum Holdings, L.P. |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 30.00% | 30.00% | 30.00% |  |
JAM Partners L.P. |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 0.00% | 11.10% |  |  |
Minimum | Tuckerman Capital Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 14.50% | 17.50% |  |  |
Minimum | Enlightenment Capital Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 9.60% | 10.00% |  |  |
Minimum | Kudu Investments |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 3.20% | 3.20% |  |  |
Maximum | Tuckerman Capital Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 62.20% | 62.40% |  |  |
Maximum | Enlightenment Capital Funds |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 66.70% | 38.40% |  |  |
Maximum | Kudu Investments |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership interest (as a percent) | 35.00% | 30.00% |  |  |

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