Equity Method Eligible Investments - Carrying Value and Ownership Percentages (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Kudu’s Participation Contracts
Investments in and Advances to Affiliates [Line Items]
Carrying Value	$ 890.5	$ 695.9
Investment in MediaAlpha
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	34.90%	27.10%
Carrying Value	$ 254.9	$ 168.6
PassportCard/DavidShield
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	53.80%	53.80%
Carrying Value	$ 150.0	$ 135.0
Elementum Holdings, L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership Interest	26.60%	29.70%
Carrying Value	$ 35.0	$ 30.0
Other equity method eligible investments, at fair value
Investments in and Advances to Affiliates [Line Items]
Carrying Value	291.7	84.4
Other equity method eligible investments, at fair value
Investments in and Advances to Affiliates [Line Items]
Carrying Value	$ 24.8	$ 0.0
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%