Equity Method Eligible Investments - Carrying Value and Ownership Percentages (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	May 07, 2020	May 06, 2020	May 31, 2019
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	$ 1,377.8	$ 786.8
Equity Method Investments
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	17.8	15.2
Kudu's Participation Contracts
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	$ 669.5	$ 400.6
Kudu's Participation Contracts | Minimum
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	3.20%	3.20%
Kudu's Participation Contracts | Maximum
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	32.00%	35.00%
MediaAlpha
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	28.00%	35.00%
Other long-term investments	$ 261.6	$ 802.2
PassportCard/DavidShield
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	53.80%	53.80%	53.80%	50.00%
Other long-term investments	$ 120.0	$ 95.0
Elementum Holdings, L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	29.70%	28.90%			30.00%
Other long-term investments	$ 45.0	$ 55.1
Other Investment Sector
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	$ 109.3	$ 132.2