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Investment Securities - Investment Holding Common Equities/ Other Investments/ MediaAlpha (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Common equity securities
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	$ 599.0	$ 660.6
Gross Unrealized Gains	64.1	26.7
Gross Unrealized Losses	(1.8)	(8.4)
Net Foreign Currency Gains (Losses)	(6.2)	(10.5)
Common equity securities, at fair value	655.1	668.4
Marketing Technology (MediaAlpha)
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	59.2	0.0
Gross Unrealized Gains	176.5	168.6
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	0.0	0.0
Common equity securities, at fair value	235.7	168.6
Other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	1,593.3	1,340.8
Gross Unrealized Gains	337.5	271.1
Gross Unrealized Losses	(104.7)	(107.1)
Net Foreign Currency Gains (Losses)	(11.1)	(16.8)
Common equity securities, at fair value	$ 1,815.0	$ 1,488.0

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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