Equity-Method Eligible Investments - Equity Method Investments Financial Data (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Total assets	$ 7,545.0		$ 7,545.0		$ 7,000.7
Total liabilities	3,678.7		3,678.7		3,296.0
Total revenues	383.2	$ (92.4)	720.3	$ 353.4
Net income (loss)	888.2	(371.4)	752.4	(308.2)
Marketing Technology (MediaAlpha)
Schedule of Equity Method Investments [Line Items]
Total assets	265.2		265.2		289.8
Total liabilities	333.6		333.6		$ 351.4
Total revenues	89.0	152.7	335.1	483.7
Total expenses	110.2	157.0	379.2	488.2
Net income (loss)	$ (21.2)	$ (4.3)	$ (44.1)	$ (4.5)