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Financial Instruments (Narrative) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Mar. 31, 2023 | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 08, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Interest rate |  |  |  | 4.40%
Unsecured Notes Two | Revolving Credit Facility |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Drawn down amount under credit facility |  | $ 200.0 | $ 200.0 |
Clearwater, Florida Office Building | Disposal Group, Disposed of by Sale, Not Discontinued Operations |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Sale price of fixed asset | $ 19.6 |  |  |
Promissory note received from sale of fixed asset | $ 9.8 |  |  |
Promissory Note |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Interest rate | 7.00% |  |  |
Promissory note, term (in years) | 4 years |  |  |
Unsecured debt | Level 2 |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Unsecured notes |  | 375.0 | 375.0 |
Private Equity Funds |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Unfunded commitments to VIEs |  | $ 7.0 | $ 8.0 |

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