Consolidated Balance Sheet - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current Assets [Abstract]
Cash and Cash Equivalents	$ 100.3	$ 69.1
Accounts Receivable (Less Allowance of $1.0 and $1.7)	85.1	144.4
Inventories – Net	84.6	86.7
Prepayments and Other	26.1	34.1
Total Current Assets	296.1	334.3
Property, Plant and Equipment – Net	4,210.7	3,904.4
Regulatory Assets	393.1	389.5
Equity Investments	183.3	161.1
Goodwill and Intangible Assets – Net	1.0	223.3
Other Non-Current Assets	191.6	152.4
Total Assets	5,275.8	5,165.0
Current Liabilities [Abstract]
Accounts Payable	143.5	149.8
Accrued Taxes	53.4	51.4
Accrued Interest	15.0	17.9
Long-Term Debt Due Within One Year	212.7	57.5
Other	58.7	128.5
Total Current Liabilities	483.3	405.1
Long-Term Debt	1,404.9	1,428.5
Deferred Income Taxes	213.9	223.6
Regulatory Liabilities	510.4	512.1
Defined Benefit Pension and Other Postretirement Benefit Plans	162.4	177.3
Other Non-Current Liabilities	293.1	262.6
Total Liabilities	3,068.0	3,009.2
Commitments, Guarantees and Contingencies (Note 7)
Shareholders’ Equity [Abstract]
Common Stock Without Par Value, 80.0 Shares Authorized, 51.7 and 51.5 Shares Issued and Outstanding	1,435.1	1,428.5
Accumulated Other Comprehensive Loss	(26.8)	(27.3)
Retained Earnings	799.5	754.6
Total Shareholders’ Equity	2,207.8	2,155.8
Total Liabilities and Shareholders' Equity	$ 5,275.8	$ 5,165.0