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