Equity Securities - (Summary of Cumulative Gross Unrealized Gains and Cumulative Gross Unrealized Losses and Impairments) (Details) - Non Marketable Equity Securities - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Equity Securities without Readily Determinable Fair Value [Line Items]
Cumulative gross unrealized gains	$ 243.5	$ 243.3
Cumulative gross unrealized losses and impairments	$ 322.4	$ 322.4

Amount of cumulative loss from downward price adjustment on investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

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- Definition

Amount of cumulative gain from upward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-3

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