Fair Value (Fair Value of Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Level 1 [Member]
Total Assets	$ 7.4	$ 7.5
Level 1 [Member] \| Subsidiaries [Member]
Total Assets	7.4	7.5
Level 2 [Member]
Total Assets	0.0	0.0
Level 2 [Member] \| Subsidiaries [Member]
Total Assets	0.0	0.0
Level 3 [Member]
Total Assets	0.0	0.0
Level 3 [Member] \| Subsidiaries [Member]
Total Assets	0.0	0.0
Fair Value [Member]
Total Assets	7.4	7.5
Fair Value [Member] \| Subsidiaries [Member]
Total Assets	7.4	7.5
Money Market Funds [Member] \| Level 1 [Member]
Investments, Fair Value Disclosure	0.3	0.5
Money Market Funds [Member] \| Level 1 [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	0.3	0.5
Money Market Funds [Member] \| Level 2 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Money Market Funds [Member] \| Level 2 [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	0.0	0.0
Money Market Funds [Member] \| Level 3 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Money Market Funds [Member] \| Level 3 [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	0.0	0.0
Money Market Funds [Member] \| Fair Value [Member]
Investments, Fair Value Disclosure	0.3	0.5
Money Market Funds [Member] \| Fair Value [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	0.3	0.5
Debt [Member] \| Level 1 [Member]
Debt	0.0	0.0
Debt [Member] \| Level 1 [Member] \| Subsidiaries [Member]
Debt	0.0	0.0
Debt [Member] \| Level 2 [Member]
Debt	1,392.0	1,376.4
Debt [Member] \| Level 2 [Member] \| Subsidiaries [Member]
Debt	623.3	610.9
Debt [Member] \| Level 3 [Member]
Debt	17.0	17.0
Debt [Member] \| Level 3 [Member] \| Subsidiaries [Member]
Debt		17.0
Debt [Member] \| Fair Value [Member]
Debt	1,409.0	1,393.4
Debt [Member] \| Fair Value [Member] \| Subsidiaries [Member]
Debt	640.3	627.9
Mutual Fund \| Level 1 [Member]
Investments, Fair Value Disclosure	7.1	7.0
Mutual Fund \| Level 1 [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	7.1	7.0
Mutual Fund \| Level 2 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Mutual Fund \| Level 2 [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	0.0	0.0
Mutual Fund \| Level 3 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Mutual Fund \| Level 3 [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	0.0	0.0
Mutual Fund \| Fair Value [Member]
Investments, Fair Value Disclosure	7.1	7.0
Mutual Fund \| Fair Value [Member] \| Subsidiaries [Member]
Investments, Fair Value Disclosure	$ 7.1	$ 7.0

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

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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-Publisher FASB
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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

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-Publisher FASB
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-SubTopic 10
-Section 50
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