CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and Cash Equivalents, at Carrying Value	$ 67.5	$ 0.0
Accounts receivable, less reserve of $2.0 and $1.5, respectively	159.0	153.8
Accrued unbilled revenues	93.7	64.7
Advances to parent	397.6	304.8
Fuel inventories	42.7	46.3
Materials and supplies, at average cost	98.8	90.6
Fuel clause under recoveries	0.0	39.5
Other	26.4	19.6
Total current assets	885.7	719.3
OTHER PROPERTY AND INVESTMENTS	4.6	4.7
PROPERTY, PLANT AND EQUIPMENT
In service	12,999.4	12,765.0
Construction work in progress	124.0	141.6
Total property, plant and equipment	13,123.4	12,906.6
Less: accumulated depreciation	3,957.3	3,868.1
Net property, plant and equipment	9,166.1	9,038.5
DEFERRED CHARGES AND OTHER ASSETS
Regulatory assets	299.4	306.0
Other	11.8	8.1
Total deferred charges and other assets	311.2	314.1
TOTAL ASSETS	10,367.6	10,076.6
Liabilities, Current [Abstract]
Accounts payable	130.0	175.0
Customer deposits	82.7	83.0
Accrued taxes	46.2	41.9
Accrued interest	40.2	37.9
Accrued compensation	28.1	29.5
Fuel clause over recoveries	37.2	4.8
Other	41.2	65.1
Total current liabilities	405.6	437.2
Long-term Debt, Excluding Current Maturities	3,493.4	3,195.2
Liabilities, Other than Long-term Debt, Noncurrent [Abstract]
Accrued benefit obligations	127.4	133.3
Deferred income taxes	974.9	951.4
Deferred investment tax credits	7.1	7.1
Regulatory Liability, Noncurrent	1,206.2	1,223.5
Other	169.3	170.6
Liabilities, Other than Long-term Debt, Noncurrent, Total	2,484.9	2,485.9
Liabilities, Total	6,383.9	6,118.3
COMMITMENTS AND CONTINGENCIES (NOTE 11)
Stockholders' Equity Attributable to Parent [Abstract]
Common stockholder's equity	1,038.2	1,036.6
Retained earnings	2,945.5	2,921.7
Stockholders' Equity Attributable to Parent, Total	3,983.7	3,958.3
TOTAL LIABILITIES AND STOCKHOLDER'S EQUITY	$ 10,367.6	$ 10,076.6