Equity Method Eligible Investments - Carrying Value and Ownership Percentages (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Kudu’s Participation Contracts
Investments in and Advances to Affiliates [Line Items]
Carrying Value	$ 1,008.4	$ 890.5
Investment in MediaAlpha
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	26.60%	34.90%
Carrying Value	$ 201.6	$ 254.9
PassportCard/DavidShield
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	53.80%	53.80%
Carrying Value	$ 150.0	$ 150.0
Elementum
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	26.60%	26.60%
Carrying Value	$ 35.0	$ 35.0
Other equity method eligible investments, at fair value
Investments in and Advances to Affiliates [Line Items]
Carrying Value	243.7	291.7
Other equity method eligible investments, at fair value
Investments in and Advances to Affiliates [Line Items]
Carrying Value	$ 0.0	$ 24.8
Minimum | Kudu’s Participation Contracts
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	4.10%	4.10%
Maximum | Kudu’s Participation Contracts
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	30.00%	30.00%