CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2,069.8		$ 2,175.5	$ 2,211.7
Revenues from Alternative Revenue Programs		52.5		56.1	58.6
OPERATING REVENUES
Total operating revenues		2,122.3		2,231.6	2,270.3
Total cost of sales		644.6		786.9	892.5
OPERATING EXPENSES
Other operation and maintenance		462.8		491.8	474.6
Depreciation and amortization		391.3		355.0	321.6
Taxes other than income		101.4		93.6	92.0
Operating expenses		955.5		940.4	888.2
Operating income (loss)		522.2		504.3	489.6
OTHER INCOME (EXPENSE)
Equity in earnings (losses) of unconsolidated affiliates	[1]	(668.0)	[2]	113.9	152.8
Allowance for equity funds used during construction		4.8		4.5	23.8
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		(3.9)		(9.8)	(10.8)
Other income		37.5		21.9	21.7
Other expense		(35.2)		(23.5)	(23.4)
Net other income (expense)		(664.8)		107.0	164.1
INTEREST EXPENSE
Interest on long-term debt		152.8		138.3	157.4
Allowance for borrowed funds used during construction		(1.9)		(2.8)	(11.7)
Interest on short-term debt and other interest charges		7.6		12.4	10.3
Interest expense		158.5		147.9	156.0
INCOME (LOSS) BEFORE TAXES		(301.1)		463.4	497.7
INCOME TAX EXPENSE (BENEFIT)		(127.4)		29.8	72.2
NET INCOME (LOSS)		$ (173.7)		$ 433.6	$ 425.5
BASIC AVERAGE COMMON SHARES OUTSTANDING		200.1		200.1	199.7
DILUTED AVERAGE COMMON SHARES OUTSTANDING		200.1		200.7	200.5
BASIC EARNINGS (LOSS) PER AVERAGE COMMON SHARE		$ (0.87)		$ 2.17	$ 2.13
DILUTED EARNINGS (LOSS) PER AVERAGE COMMON SHARE		(0.87)		2.16	2.12
DIVIDENDS DECLARED PER COMMON SHARE		$ 1.5800		$ 1.5050	$ 1.3950
Other Comprehensive Income (Loss), Net of Tax		$ (4.2)		$ 1.0	$ (5.7)
Og and E [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		2,069.8		2,175.5	2,211.7
Revenues from Alternative Revenue Programs		52.5		56.1	58.6
OPERATING REVENUES
Total operating revenues		2,122.3		2,231.6	2,270.3
Total cost of sales		644.6		786.9	892.5
OPERATING EXPENSES
Other operation and maintenance		464.4		492.5	473.8
Depreciation and amortization		391.3		355.0	321.6
Taxes other than income		97.2		89.5	88.2
Operating expenses		952.9		937.0	883.6
Operating income (loss)		524.8		507.7	494.2
OTHER INCOME (EXPENSE)
Allowance for equity funds used during construction		4.8		4.5	23.8
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		(3.1)		(1.2)	(8.9)
Other income		5.0		6.7	14.1
Other expense		(2.6)		(6.9)	(3.4)
Net other income (expense)		4.1		3.1	25.6
INTEREST EXPENSE
Interest on long-term debt		152.8		138.3	157.4
Allowance for borrowed funds used during construction		(1.9)		(2.8)	(11.7)
Interest on short-term debt and other interest charges		3.9		5.0	6.1
Interest expense		154.8		140.5	151.8
INCOME (LOSS) BEFORE TAXES		374.1		370.3	368.0
INCOME TAX EXPENSE (BENEFIT)		34.7		20.1	40.0
Net Income (Loss) Attributable to Parent		339.4		350.2	328.0
Other Comprehensive Income (Loss), Net of Tax		0.0		0.0	0.0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		$ 339.4		$ 350.2	$ 328.0

[1] For the year ended December 31, 2020, Enable recorded a $225.0 million impairment on its SESH equity method investment. Enable estimated the fair value of this equity method investment was below the carrying value at September 30, 2020 and concluded the decline in value was other than temporary due to the expiration of a transportation contract and the current status of renewal negotiations. The impairment ran through OGE Energy's portion of Enable net income and was offset by basis differences that flow through the amortization of basis difference and dilution recognition line item above.

[2] In March 2020, OGE Energy recorded a $780.0 million impairment on its investment in Enable, as further discussed in Notes 5 and 7.