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Significant Transactions - MediaAlpha (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Mar. 23, 2021 | Oct. 30, 2020 | Dec. 31, 2022 | Dec. 31, 2021
MediaAlpha |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |
Ownership interest (as a percent) |  |  | 27.10% | 28.00%
Share price (in USD per share) |  |  | $ 9.95 |
Investment in MediaAlpha, at fair value |  |  | $ 168.6 |
Other Operations |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |
Investment in MediaAlpha, at fair value |  |  | $ 168.6 | $ 261.6
Secondary Offering | MediaAlpha |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) | 8,050 |  |  |
Sale of stock, price per share (in USD per share) | $ 46.00 |  |  |
Sale of stock, price per share net of underwriting fees (in dollars per share) | $ 44.62 |  |  |
MediaAlpha |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |
Investment owned (in shares) |  |  | 16,900 |
Fully diluted ownership interest (as a percent) |  |  | 25.10% |
MediaAlpha | IPO |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) |  | 3,600 |  |
Sale of stock, price per share (in USD per share) |  | $ 19.00 |  |
Sale of stock, price per share net of underwriting fees (in dollars per share) |  | $ 17.67 |  |
Sale of stock, consideration received in transaction |  | $ 63.8 |  |
Proceeds from dividends received |  | $ 55.0 |  |
Increase in investment owned (in dollars per share) |  |  | $ 1.00 |
Increase in book value per share (in dollars per share) |  |  | $ 6.60 |
MediaAlpha | Secondary Offering |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) | 3,600 |  |  |
Sale of stock, consideration received in transaction | $ 160.3 |  |  |

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