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Investment Securities - Investment Holding Common Equities/ Other Investments/ MediaAlpha (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Common equity securities
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	$ 660.6	$ 660.6
Gross Unrealized Gains	48.0	26.7
Gross Unrealized Losses	(2.8)	(8.4)
Net Foreign Currency Gains (Losses)	(8.0)	(10.5)
Common equity securities, at fair value	697.8	668.4
Marketing Technology (MediaAlpha)
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	0.0	0.0
Gross Unrealized Gains	253.8	168.6
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	0.0	0.0
Common equity securities, at fair value	253.8	168.6
Other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	1,489.7	1,340.8
Gross Unrealized Gains	264.3	271.1
Gross Unrealized Losses	(96.2)	(107.1)
Net Foreign Currency Gains (Losses)	(14.8)	(16.8)
Common equity securities, at fair value	$ 1,643.0	$ 1,488.0

X

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
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