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Fair Value Measurements - Balance Sheet Grouping (Details) - USD ($) $ in Millions | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | $ 22.2 | $ 22.5
Unfunded Commitments | 1.7 | 0.0
Reported Value Measurement |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 89.0 | 91.3
Unfunded Commitments | 1.7 | 0.0
Unfunded Commitments | 230.2 | 221.9
Mezzanine Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 39.5 | 40.8
Unfunded Commitments | 69.3 | 67.0
Real Estate Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 0.1 | 0.0
Senior Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 47.0 | 48.2
Unfunded Commitments | 6.9 | 8.4
Leveraged Buyout |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 0.6 | 0.6
Unfunded Commitments | 39.0 | 30.4
Secondary Transactions |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 1.7 | 1.6
Unfunded Commitments | 1.6 | 1.6
Distressed Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 0.0 | 0.0
Unfunded Commitments | 15.7 | 15.0
Equity Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 6.8 | 8.0
Other Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Unfunded Commitments | 0.1 | 0.1
Unfunded Commitments | 0.2 | 0.2
Measured at Net Asset Value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 1.8 | 1.8
Measured at Net Asset Value | Reported Value Measurement |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 176.2 | 186.3
Fair Value Using NAV | 198.4 | 183.6
Unfunded Commitments | 139.5 | 130.6
Fair Value Using NAV | 1.8 | 1.8
Fair Value Using NAV | 376.4 | 371.7
Measured at Net Asset Value | Mezzanine Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 115.3 | 116.7
Fair Value Using NAV | 115.7 | 116.9
Measured at Net Asset Value | Real Estate Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 24.3 | 27.3
Measured at Net Asset Value | Senior Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 19.1 | 19.1
Fair Value Using NAV | 27.5 | 26.3
Measured at Net Asset Value | Leveraged Buyout |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 7.1 | 7.5
Fair Value Using NAV | 32.6 | 19.2
Measured at Net Asset Value | Secondary Transactions |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 3.9 | 5.5
Fair Value Using NAV | 2.0 | 2.4
Measured at Net Asset Value | Distressed Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 1.4 | 4.4
Fair Value Using NAV | 11.0 | 11.7
Measured at Net Asset Value | Equity Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 9.2 | 7.0
Measured at Net Asset Value | Other Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fair Value Using NAV | 5.1 | 5.8
Fair Value Using NAV | $ 0.4 | $ 0.1

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- Definition Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 28 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-28 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 8: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 107 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-107 Reference 9: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 103 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-103 Reference 10: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 35 -Paragraph 54B -Publisher FASB -URI https://asc.fasb.org/1943274/2147482134/820-10-35-54B Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A + Details
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