Equity Method Eligible Investments - Ownership Interests and Carrying Values (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Kudu's Participation Contracts
Investments in unconsolidated affiliates
Carrying Value	$ 775.3	$ 695.9
Kudu's Participation Contracts | Minimum
Investments in unconsolidated affiliates
Ownership Interest	4.10%	4.10%
Kudu's Participation Contracts | Maximum
Investments in unconsolidated affiliates
Ownership Interest	30.00%	30.00%
MediaAlpha
Investments in unconsolidated affiliates
Ownership Interest	35.30%	27.10%
Carrying Value	$ 188.8	$ 168.6
PassportCard/DavidShield
Investments in unconsolidated affiliates
Ownership Interest	53.80%	53.80%
Carrying Value	$ 150.0	$ 135.0
Elementum Holdings, L.P.
Investments in unconsolidated affiliates
Ownership Interest	26.60%	29.70%
Carrying Value	$ 35.0	$ 30.0
Other equity method eligible investments, at fair value
Investments in unconsolidated affiliates
Carrying Value	279.0	84.4
Other equity method eligible investments, at fair value
Investments in unconsolidated affiliates
Carrying Value	$ 25.2	$ 0.0