CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 1.5	$ 1.1	$ 32.0	$ 0.0
Accounts Receivable, after Allowance for Credit Loss, Current	242.3	157.8
Accrued unbilled revenues	82.5	67.6
Fuel inventories	(35.0)	(36.5)
Income taxes receivable	0.5	8.1
Materials and supplies, at average cost	111.4	116.2
Fuel clause under recoveries	98.2	0.0
Other	55.6	41.2
Total current assets	627.0	428.5
OTHER PROPERTY AND INVESTMENTS
Investment in unconsolidated affiliates	478.9	397.4	376.8
Other	90.8	86.7
Total other property and investments	569.7	484.1
PROPERTY, PLANT AND EQUIPMENT
In service	13,703.9	13,296.7
Construction work in progress	249.3	145.5
Total property, plant and equipment	13,953.2	13,442.2
Less: accumulated depreciation	4,257.3	4,067.6
Property, Plant and Equipment, Net	9,695.9	9,374.6
DEFERRED CHARGES AND OTHER ASSETS
Regulatory assets	1,264.9	415.6
Other	20.0	16.0
Total deferred charges and other assets	1,284.9	431.6
TOTAL ASSETS	12,177.5	10,718.8	10,497.6
CURRENT LIABILITIES
Short-term Debt	383.2	95.0
Accounts payable	243.5	251.5
Dividends payable	82.1	80.5
Customer deposits	80.6	81.1
Accrued taxes	82.8	55.7
Accrued interest	42.5	40.2
Accrued compensation	38.6	31.1
Fuel clause over recoveries	0.0	28.6
Other	40.6	33.7
Total current liabilities	993.9	697.4
LONG-TERM DEBT	4,495.8	3,494.4
DEFERRED CREDITS AND OTHER LIABILITIES
Accrued benefit obligations	175.2	231.4
Deferred income taxes	1,240.9	1,268.6
Deferred investment tax credits	11.0	10.9
Regulatory liabilities	1,247.7	1,188.9
Other	198.1	195.4
Total deferred credits and other liabilities	2,872.9	2,895.2
Total liabilities	8,362.6	7,087.0
COMMITMENTS AND CONTINGENCIES (NOTE 14)
STOCKHOLDERS' EQUITY
Common stockholders' equity	1,123.0	1,124.6
Retained earnings	2,718.3	2,544.6
Accumulated other comprehensive loss, net of tax	(26.3)	(32.1)	(25.7)	(27.9)
Total stockholders' equity	3,814.9	3,631.8
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	12,177.5	10,718.8
Treasury Stock, Carrying Basis	(0.1)	(5.3)
Accounts Receivable, Allowance for Credit Loss	2.4	2.6
OG&E [Member]
CURRENT ASSETS
Cash and cash equivalents	1.5	0.0	32.0	0.0
Accounts Receivable, after Allowance for Credit Loss, Current	242.3	156.3
Accrued unbilled revenues	82.5	67.7
Advances to parent	0.0	272.0
Fuel inventories	(35.0)	(36.5)
Materials and supplies, at average cost	111.4	116.2
Fuel clause under recoveries	98.2	0.0
Other	49.4	36.9
Total current assets	620.3	685.6
OTHER PROPERTY AND INVESTMENTS
Total other property and investments	3.9	4.1
PROPERTY, PLANT AND EQUIPMENT
In service	13,697.8	13,290.6
Construction work in progress	249.3	145.5
Total property, plant and equipment	13,947.1	13,436.1
Less: accumulated depreciation	4,257.3	4,067.6
Property, Plant and Equipment, Net	9,689.8	9,368.5
DEFERRED CHARGES AND OTHER ASSETS
Regulatory assets	1,264.9	415.6
Other	19.0	15.2
Total deferred charges and other assets	1,283.9	430.8
TOTAL ASSETS	11,597.9	10,489.0
CURRENT LIABILITIES
Accounts payable	230.7	236.7
Advances from parent	42.2	0.0
Customer deposits	80.6	81.1
Accrued taxes	76.1	53.3
Accrued interest	41.3	40.2
Accrued compensation	28.1	22.5
Fuel clause over recoveries	0.0	28.6
Other	40.4	33.5
Total current liabilities	539.4	495.9
LONG-TERM DEBT	3,995.9	3,494.4
DEFERRED CREDITS AND OTHER LIABILITIES
Accrued benefit obligations	93.5	135.4
Deferred income taxes	981.5	1,020.8
Deferred investment tax credits	11.0	10.9
Regulatory liabilities	1,247.7	1,188.9
Other	166.5	167.1
Total deferred credits and other liabilities	2,500.2	2,523.1
Total liabilities	7,035.5	6,513.4
STOCKHOLDERS' EQUITY
Common stockholders' equity	1,571.2	1,039.5
Retained earnings	2,991.2	2,936.1
Total stockholders' equity	4,562.4	3,975.6	$ 3,933.8	$ 3,958.3
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 11,597.9	$ 10,489.0