Fair Value (Fair Value and Cost of Non-Derivative Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Long-term Debt	$ 1,535.6	$ 1,395.5
Subsidiaries [Member]
Long-term Debt	712.9	574.3
Cost [Member]
Total Assets	5.9	6.1
Cost [Member] | Subsidiaries [Member]
Total Assets	5.9	6.1
Fair Value [Member]
Total Assets	7.2	9.4
Fair Value [Member] | Subsidiaries [Member]
Total Assets	7.2	9.4
Money Market Funds [Member] | Cost [Member]
5900000	0.4	0.4
Money Market Funds [Member] | Cost [Member] | Subsidiaries [Member]
5900000	0.4	0.4
Money Market Funds [Member] | Fair Value [Member]
Investments, Fair Value Disclosure	0.4	0.4
Money Market Funds [Member] | Fair Value [Member] | Subsidiaries [Member]
Investments, Fair Value Disclosure	0.4	0.4
Equity Securities [Member] | Cost [Member]
5900000	1.8	1.9
Equity Securities [Member] | Cost [Member] | Subsidiaries [Member]
5900000	1.8	1.9
Equity Securities [Member] | Fair Value [Member]
Investments, Fair Value Disclosure	3.6	5.1
Equity Securities [Member] | Fair Value [Member] | Subsidiaries [Member]
Investments, Fair Value Disclosure	3.6	5.1
Debt Securities [Member] | Cost [Member]
5900000	3.7	3.8
Debt Securities [Member] | Cost [Member] | Subsidiaries [Member]
5900000	3.7	3.8
Debt Securities [Member] | Fair Value [Member]
Investments, Fair Value Disclosure	3.2	3.9
Debt Securities [Member] | Fair Value [Member] | Subsidiaries [Member]
Investments, Fair Value Disclosure	$ 3.2	$ 3.9