Fair Value Measurements (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Trading Securities at Fair Value	$ 84.5	$ 98.6
Investments, Fair Value Disclosure	51.9
Fair Value, Measurements, Recurring [Member]
Investments, Fair Value Disclosure	96.0	115.0
Total Assets at Fair Value	96.0	115.0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Investments, Fair Value Disclosure	96.0	115.0
Total Assets at Fair Value	96.0	115.0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Total Assets at Fair Value	0.0	0.0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Total Assets at Fair Value	0.0	0.0
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Marketable Securities	11.3	16.2
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Marketable Securities	11.3	16.2
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Marketable Securities	0.0	0.0
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Marketable Securities	0.0	0.0
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member]
Trading Securities at Fair Value	84.5	98.6
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Trading Securities at Fair Value	84.5	98.6
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Trading Securities at Fair Value	0.0	0.0
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Trading Securities at Fair Value	0.0	0.0
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Marketable Securities	0.2	0.2
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Marketable Securities	0.2	0.2
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Marketable Securities	0.0	0.0
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Marketable Securities	$ 0.0	$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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Amount of investment in marketable security.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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