Investment Securities - Common Equity Securities and Other Long Term Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Common equity securities
Cost or Amortized Cost	$ 384.3	$ 537.0
Gross Unrealized Gains	99.9	120.4
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	(1.2)	(7.4)
Carrying Value	483.0	650.0
Other long-term investments
Cost or Amortized Cost	2,378.8	1,748.7
Gross Unrealized Gains	712.6	546.4
Gross Unrealized Losses	(123.1)	(116.7)
Net Foreign Currency Gains (Losses)	(9.8)	(28.2)
Carrying Value	2,958.5	2,150.2
MediaAlpha
Investment in MediaAlpha
Cost or Amortized Cost	59.2	59.2
Gross Unrealized Gains	172.0	142.4
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	0.0	0.0
Carrying Value	$ 231.2	$ 201.6