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Equity-Method Eligible Investments - Significant Equity Method Eligible Investments (Details) | Mar. 31, 2021 | Dec. 31, 2020 | May 07, 2020 | May 06, 2020
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PassportCard/DavidShield |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 53.80% | 53.80% | 53.80% | 50.00%
New Market Solutions, LLC |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 46.70% | 46.70% |  |
durchblicker |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 45.00% | 45.00% |  |
MediaAlpha |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 28.50% | 35.00% |  |
Elementum Holdings L.P. |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 29.70% | 28.90% |  |
Compare.com |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 18.40% | 18.40% |  |
Minimum | Tuckerman Capital Funds |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 16.10% | 14.90% |  |
Minimum | Enlightenment Capital Funds |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 9.10% | 9.70% |  |
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) | 30.00% | 62.00% |  |
Maximum | Enlightenment Capital Funds |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 66.30% | 66.70% |  |
Maximum | Kudu Investments |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership interest (as a percent) | 35.60% | 35.00% |  |

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 + Details
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