Investment Securities - Investment Holding Common Equities/ Other Investments/ MediaAlpha (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Common equity securities
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	$ 274.3	$ 236.3
Gross Unrealized Gains	20.9	16.1
Gross Unrealized Losses	(6.7)	0.0
Net Foreign Currency Gains (Losses)	(9.9)	(1.3)
Common equity securities, at fair value	278.6	251.1
Marketing Technology (MediaAlpha)
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	0.0	0.0
Gross Unrealized Gains	166.9	261.6
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	0.0	0.0
Common equity securities, at fair value	166.9	261.6
Other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	1,264.2	1,186.7
Gross Unrealized Gains	295.6	239.0
Gross Unrealized Losses	(81.1)	(44.1)
Net Foreign Currency Gains (Losses)	(10.0)	(3.8)
Common equity securities, at fair value	$ 1,468.7	$ 1,377.8