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Fair Value (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Fair Value Disclosure [Line Items]
Transfers between Fair Value Hierarchies		$ 0.0	$ 0.0
Allowance for Credit Loss	$ 0.3		0.3	$ 0.6
Debt Securities, Available-for-Sale, Realized Gain	0.1		0.5
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Allowance for Credit Loss	0.0		0.0	0.0
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Allowance for Credit Loss	$ 0.3		$ 0.3	$ 0.6

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479106/326-30-50-9

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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-Name Accounting Standards Codification
-Section 50
-Paragraph 9
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479106/326-30-50-9

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

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