Equity-Method Eligible Investments - Carrying Values of Equity Method Eligible Investments Recorded within Other Long-Term Investments (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Investments in unconsolidated affiliates
Other long-term investments	$ 1,815.0	$ 1,488.0
Kudu investments
Investments in unconsolidated affiliates
Other long-term investments	$ 737.1	$ 695.9
Kudu investments | Minimum
Investments in unconsolidated affiliates
Ownership interest (as a percent)	4.10%	4.10%
Kudu investments | Maximum
Investments in unconsolidated affiliates
Ownership interest (as a percent)	30.00%	30.00%
Marketing Technology (MediaAlpha)
Investments in unconsolidated affiliates
Ownership interest (as a percent)	35.70%	27.10%
Other long-term investments	$ 235.7	$ 168.6
PassportCard/DavidShield
Investments in unconsolidated affiliates
Ownership interest (as a percent)	53.80%	53.80%
Other long-term investments	$ 150.0	$ 135.0
Elementum Holdings, L.P.
Investments in unconsolidated affiliates
Ownership interest (as a percent)	26.60%	29.70%
Other long-term investments	$ 30.0	$ 30.0
Other
Investments in unconsolidated affiliates
Other long-term investments	263.4	84.4
Equity Method Investments
Investments in unconsolidated affiliates
Other long-term investments	$ 24.9	$ 0.0