OGE Energy (OGE) 10-K 25 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020
Document Information [Line Items]
Entity Registrant Name	OGE ENERGY CORP.
Entity Central Index Key	0001021635
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	200,021,161	200,169,838
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float		$ 6,077,156,282
Entity Incorporation, State or Country Code	OK
Entity Tax Identification Number	73-1481638
Entity Address, Address Line One	321 North Harvey
Entity Address, Address Line Two	P.O. Box 321
Trading Symbol	OGE
Security Exchange Name	NYSE
Entity Interactive Data Current	Yes
City Area Code	405
Local Phone Number	553-3000
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	73101-0321
Entity File Number	1-12579
Title of 12(b) Security	Common Stock
Entity Address, City or Town	Oklahoma City
Share Price		$ 30.36
Document Transition Report	false
Document Annual Report	true
ICFR Auditor Attestation Flag	true
Og and E [Member]
Document Information [Line Items]
Entity Registrant Name	OKLAHOMA GAS AND ELECTRIC COMPANY
Entity Central Index Key	0000074145
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	40,378,745
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Tax Identification Number	73-0382390
Entity Interactive Data Current	Yes
Entity File Number	1-1097
ICFR Auditor Attestation Flag	true

CONSOLIDATED STATEMENTS OF INCO

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	321.6
Taxes other than income		101.4		93.6	92
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)	[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	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
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	$ (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	321.6
Taxes other than income		97.2		89.5	88.2
Operating expenses		952.9		937	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		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	6.1
Interest expense		154.8		140.5	151.8
INCOME (LOSS) BEFORE TAXES		374.1		370.3	368
INCOME TAX EXPENSE (BENEFIT)		34.7		20.1	40
Net Income (Loss) Attributable to Parent		339.4		350.2	328
Other Comprehensive Income (Loss), Net of Tax		0		0	0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		$ 339.4		$ 350.2	$ 328
[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.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income (loss)	$ (173.7)	$ 433.6	$ 425.5
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $1.2, $1.1 and $1.1, respectively	3.9	3.4	3.3
Net loss arising during the period, net of tax of ($1.7), ($2.6) and ($4.7), respectively	(5.1)	(8.3)	(14.1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax	2.2	8.6	4.7
Postretirement benefit plans:
Amortization of prior service credit, net of tax of ($0.6), ($0.6) and ($0.6), respectively	(1.7)	(1.7)	(1.7)
Amortization of deferred net gain, net of tax of $0.0, $0.0 and $0.0, respectively	(0.1)	(0.2)	0
Net gain (loss) arising during the period, net of tax of ($0.8), ($0.1) and $0.7, respectively	(2.4)	(0.2)	2.1
Curtailment cost, net of tax of ($0.1), $0.0 and $0.0, respectively	(0.3)	0	0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	(0.2)	(0.2)	0
Other comprehensive income (loss), net of tax	(4.2)	1	(5.7)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0.7	0.6	0
Comprehensive income (loss)	$ (177.9)	$ 434.6	$ 419.8

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Parenthetical - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $1.2, $1.1 and $1.1, respectively	$ 1.2	$ 1.1	$ 1.1
Net loss arising during the period, net of tax of ($1.7), ($2.6) and ($4.7), respectively	(1.7)	(2.6)	(4.7)
Postretirement plans:
Amortization of deferred net gain, net of tax of $0.0, $0.0 and $0.0, respectively	0	0	0
Net gain (loss) arising during the period, net of tax of ($0.8), ($0.1) and $0.7, respectively	(0.8)	(0.1)	0.7
Amortization of prior service credit, net of tax of ($0.6), ($0.6) and ($0.6), respectively	(0.6)	(0.6)	(0.6)
Pension Plans [Member]
Pension Plan and Restoration of Retirement Income Plan:
Settlement cost, net of tax of $0.7, $2.7 and $1.6, respectively	0.7	2.7	1.6
Other Postretirement Benefits Plan [Member]
Pension Plan and Restoration of Retirement Income Plan:
Settlement cost, net of tax of $0.7, $2.7 and $1.6, respectively	$ (0.1)	$ 0
Postretirement plans:
Curtailment cost, net of tax of ($0.1), $0.0 and $0.0, respectively			$ 0

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)		$ (173.7)		$ 433.6	$ 425.5
Adjustments to reconcile net income (loss) to net cash provided from operating activities:
Depreciation and amortization		391.3		355	321.6
Deferred income taxes and investment tax credits, net		(134.5)		27.6	78.5
Equity in (earnings) losses of unconsolidated affiliates	[1]	668	[2]	(113.9)	(152.8)
Distributions from unconsolidated affiliates		91.7		125.5	141.2
Allowance for equity funds used during construction		(4.8)		(4.5)	(23.8)
Stock-based compensation expense		9.8		13.9	13.4
Regulatory assets		112		47.1	10.8
Regulatory liabilities		(64)		(45.6)	(16.5)
Other assets		(9.2)		(3.8)	6.2
Other liabilities		(26.3)		19.2	1
Change in certain current assets and liabilities:
Accounts receivable and accrued unbilled revenues, net		3.1		18.8	19.8
Income taxes receivable		2.8		(1)	(4.1)
Fuel, materials and supplies inventories		(8.9)		4.2	27.3
Fuel recoveries		63.3		(33)	(3.4)
Other current assets		(16.8)		5.1	25.1
Accounts payable		59.8		(34.5)	29.7
Other current liabilities		(26.8)		(38)	73.2
Net cash provided from operating activities		712.8		681.5	951.1
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)		(650.5)		(635.5)	(573.6)
Investment in unconsolidated affiliates		(4.4)		(7.7)	(2.5)
Return of capital - unconsolidated affiliates		0		18.5	0
Proceeds from sale of assets		0		0	0.1
Net cash used in investing activities		(654.9)		(624.7)	(576)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (decrease) in short-term debt		(17)		112	(168.4)
Proceeds from long-term debt		297.1		296.5	396
Payment of long-term debt		(0.1)		(250.1)	(250.1)
Dividends paid on common stock		(314.9)		(299.2)	(272.2)
Cash paid for employee equity-based compensation and expense of common stock		(7.1)		(10.3)	(0.5)
Other		(0.1)		0	0
Purchase of treasury stock		(14.7)		0	0
Net cash used in financing activities		(56.8)		(151.1)	(295.2)
NET CHANGE IN CASH AND CASH EQUIVALENTS		1.1		(94.3)	79.9
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		0		94.3	14.4
CASH AND CASH EQUIVALENTS AT END OF YEAR		1.1		0	94.3
Interest costs capitalized		1.9		2.8	11.7
Interest (net of interest capitalized)		153.4		152.2	153.8
Income taxes (net of income tax refunds)		3.9		5.5	2.8
Power plant long-term service agreement		6.8		28.9	(9.2)
Og and E [Member]
Adjustments to reconcile net income (loss) to net cash provided from operating activities:
Depreciation and amortization		391.3		355	321.6
Deferred income taxes and investment tax credits, net		40.9		20.4	56.6
Allowance for equity funds used during construction		(4.8)		(4.5)	(23.8)
Stock-based compensation expense		3		4.9	4.6
Regulatory assets		112		47.1	10.8
Regulatory liabilities		(64)		(45.6)	(16.5)
Other assets		(3.4)		3.8	1.9
Other liabilities		(24.3)		8.4	0
Change in certain current assets and liabilities:
Accounts receivable and accrued unbilled revenues, net		4.5		17	19.5
Fuel, materials and supplies inventories		(8.9)		4.2	27.3
Fuel recoveries		63.3		(33)	(3.4)
Other current assets		(17.3)		5.9	23.1
Accounts payable		64.8		(30)	19
Other current liabilities		(26.8)		(35.1)	72.5
Net cash provided from operating activities		640.4		573.8	804
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)		(650.5)		(635.5)	(573.6)
Proceeds from sale of assets		0		0	0.1
Net cash used in investing activities		(650.5)		(635.5)	(573.5)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt		297.1		296.5	396
Payment of long-term debt		(0.1)		(250.1)	(250.1)
Dividends paid on common stock		(325)		0	(185)
Net cash used in financing activities		10.1		61.7	(230.5)
NET CHANGE IN CASH AND CASH EQUIVALENTS		0		0	0
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR		0		0	0
CASH AND CASH EQUIVALENTS AT END OF YEAR		0		0	0
Interest costs capitalized		1.9		2.8	11.7
Net Income (Loss) Attributable to Parent		339.4		350.2	328
Increase (Decrease) in Income Taxes Payable		(5.3)		(0.7)	(15.6)
Changes In Advances With Parent		38.1		15.3	(191.4)
Interest (net of interest capitalized)		150.2		144.6	149.7
Income taxes (net of income tax refunds)		(0.2)		1.3	0.9
Power plant long-term service agreement		$ 6.8		$ 28.9	$ (9.2)
[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.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 1.1		$ 0
Accounts receivable, after allowance for doubtful accounts	157.8		153.8
Accrued unbilled revenues	67.6		64.7
Income taxes receivable	8.1		10.9
Fuel inventories	36.5		46.3
Materials and supplies, at average cost	116.2		90.6
Fuel clause under recoveries	0		39.5
Other	41.2		24.4
Total current assets	428.5		430.2
OTHER PROPERTY AND INVESTMENTS
Investment in unconsolidated affiliates	397.4		1,151.5
Other	86.7		82.7
Total other property and investments	484.1		1,234.2
PROPERTY, PLANT AND EQUIPMENT
In service	13,296.7		12,771.1
Construction work in progress	145.5		141.6
Total property, plant and equipment	13,442.2		12,912.7
Less: accumulated depreciation	4,067.6		3,868.1
Net property, plant and equipment	9,374.6		9,044.6
DEFERRED CHARGES AND OTHER ASSETS
Regulatory assets	415.6		306
Other	16		9.3
Total deferred charges and other assets	431.6		315.3
TOTAL ASSETS	10,718.8		11,024.3
Allowance for Doubtful Accounts Receivable	2.6		1.5
CURRENT LIABILITIES
Short-term debt	95		112
Accounts payable	251.5		194.9
Dividends payable	80.5		77.6
Customer deposits	81.1		83
Accrued taxes	55.7		41.9
Accrued interest	40.2		37.9
Accrued compensation	31.1		40.6
Long-term debt due within one year	0		0
Fuel clause over recoveries	28.6		4.8
Other	33.7		65.2
Total current liabilities	697.4		657.9
LONG-TERM DEBT	3,494.4		3,195.2
DEFERRED CREDITS AND OTHER LIABILITIES
Accrued benefit obligations	231.4		225
Deferred income taxes	1,268.6		1,375.8
Accumulated Deferred Investment Tax Credit	10.9		7.1
Regulatory liabilities	1,188.9		1,223.5
Other	195.4		200.3
Total deferred credits and other liabilities	2,895.2		3,031.7
Total liabilities	7,087		6,884.8
COMMITMENTS AND CONTINGENCIES (NOTE 15)
STOCKHOLDERS' EQUITY
Common stockholders' equity	1,124.6		1,131.3
Retained earnings	2,544.6		3,036.1
Accumulated other comprehensive loss, net of tax	(32.1)		(27.9)
Stockholders' Equity Attributable to Parent	3,631.8		4,139.5
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	10,718.8		11,024.3
Og and E [Member]
CURRENT ASSETS
Cash and cash equivalents	0		0
Accounts receivable, after allowance for doubtful accounts	156.3		153.8
Accrued unbilled revenues	67.7		64.7
Advances to parent	272		304.8
Fuel inventories	36.5		46.3
Materials and supplies, at average cost	116.2		90.6
Fuel clause under recoveries	0		39.5
Other	36.9		19.6
Total current assets	685.6		719.3
OTHER PROPERTY AND INVESTMENTS
Total other property and investments	4.1		4.7
PROPERTY, PLANT AND EQUIPMENT
In service	13,290.6		12,765
Construction work in progress	145.5		141.6
Total property, plant and equipment	13,436.1		12,906.6
Less: accumulated depreciation	4,067.6		3,868.1
Net property, plant and equipment	9,368.5		9,038.5
DEFERRED CHARGES AND OTHER ASSETS
Regulatory assets	415.6		306
Other	15.2		8.1
Total deferred charges and other assets	430.8		314.1
TOTAL ASSETS	10,489		10,076.6
CURRENT LIABILITIES
Accounts payable	236.7		175
Customer deposits	81.1		83
Accrued taxes	53.3		41.9
Accrued interest	40.2		37.9
Accrued compensation	22.5		29.5
Long-term debt due within one year	0		0
Fuel clause over recoveries	28.6		4.8
Other	33.5		65.1
Total current liabilities	495.9		437.2
LONG-TERM DEBT	3,494.4		3,195.2
DEFERRED CREDITS AND OTHER LIABILITIES
Accrued benefit obligations	135.4		133.3
Deferred income taxes	1,020.8		951.4
Accumulated Deferred Investment Tax Credit	10.9		7.1
Regulatory liabilities	1,188.9		1,223.5
Other	167.1		170.6
Total deferred credits and other liabilities	2,523.1		2,485.9
Total liabilities	6,513.4		6,118.3
COMMITMENTS AND CONTINGENCIES (NOTE 15)
STOCKHOLDERS' EQUITY
Common stockholders' equity	1,039.5		1,036.6
Retained earnings	2,936.1		2,921.7
Stockholders' Equity Attributable to Parent	3,975.6		3,958.3
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 10,489		$ 10,076.6

CONSOLIDATED BALANCE SHEETS Par

CONSOLIDATED BALANCE SHEETS Parenthetical - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Allowance for Doubtful Accounts Receivable	$ 2.6	$ 1.5

CONSOLIDATED STATEMENTS OF CAPI

CONSOLIDATED STATEMENTS OF CAPITALIZATION - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule of Capitalization, Long-term Debt [Line Items]
Common Stock, Value	$ 2	$ 2
Premium on common stock	1,122.6	1,129.3
Retained earnings	2,544.6	3,036.1
Accumulated other comprehensive loss, net of tax	$ (32.1)	$ (27.9)
Treasury Stock, Common, Shares	0.1	0
Treasury Stock, Value	$ (5.3)	$ 0
Total stockholders' equity	3,631.8	4,139.5
Unamortized debt expense	(25.3)	(24.2)
Total long-term debt	3,494.4	3,195.2
Less: long-term debt due within one year	0	0
Total long-term debt (excluding long-term debt due within one year)	3,494.4	3,195.2
Total capitalization (including long-term debt due within one year)	$ 7,126.2	$ 7,334.7
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	450	450
Common Stock, Shares, Outstanding	200.1	200.1
Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Common Stock, Value	$ 100.9	$ 100.9
Premium on common stock	938.6	935.7
Retained earnings	2,936.1	2,921.7
Total stockholders' equity	3,975.6	3,958.3
Unamortized debt expense	(25.3)	(24.2)
Unamortized discount	(10.1)	(10.5)
Total long-term debt	3,494.4	3,195.2
Less: long-term debt due within one year	0	0
Total long-term debt (excluding long-term debt due within one year)	3,494.4	3,195.2
Total capitalization (including long-term debt due within one year)	$ 7,470	$ 7,153.5
Common Stock, Par or Stated Value Per Share	$ 2.50	$ 2.50
Common Stock, Shares Authorized	100	100
Common Stock, Shares, Outstanding	40.4	40.4
Garfield Industrial Authority Bond [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maturity Date	Jan. 1, 2025
Muskogee Industrial Authority Bond Due 2025 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maturity Date	Jan. 1, 2025
Muskogee Industrial Authority Bond Due 2027 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maturity Date	Jun. 1, 2027
Senior Notes [Member] | Series Due July 15, 2027 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 125	$ 125
Debt Instrument, Interest Rate, Stated Percentage	6.65%
Debt Instrument, Maturity Date	Jul. 15, 2027
Senior Notes [Member] | Series Due April 15, 2028 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 100	100
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Debt Instrument, Maturity Date	Apr. 15, 2028
Senior Notes [Member] | Series Due August 15, 2028 [Member] [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 400	400
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Senior Notes [Member] | Series Due March 15, 2030 | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 300	300
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Debt Instrument, Maturity Date	Mar. 15, 2030
Senior Notes [Member] | Series Due January 15, 2036 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 110	110
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Debt Instrument, Maturity Date	Jan. 15, 2036
Senior Notes [Member] | Series Due February 1, 2038 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 200	200
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Debt Instrument, Maturity Date	Feb. 1, 2038
Senior Notes [Member] | Series Due June 1, 2040 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 250	250
Debt Instrument, Interest Rate, Stated Percentage	5.85%
Debt Instrument, Maturity Date	Jun. 1, 2040
Senior Notes [Member] | Series Due May 15, 2041 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 250	250
Debt Instrument, Interest Rate, Stated Percentage	5.25%
Debt Instrument, Maturity Date	May 15, 2041
Senior Notes [Member] | Series Due May 1, 2043 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 250	250
Debt Instrument, Interest Rate, Stated Percentage	3.90%
Debt Instrument, Maturity Date	May 1, 2043
Senior Notes [Member] | Series Due March 15, 2044 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 250	250
Debt Instrument, Interest Rate, Stated Percentage	4.55%
Debt Instrument, Maturity Date	Mar. 15, 2044
Senior Notes [Member] | Series Due December 15, 2044 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 250	250
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Debt Instrument, Maturity Date	Dec. 15, 2044
Senior Notes [Member] | Series due August 15, 2047 [Member] [Domain] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 300	300
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Debt Instrument, Maturity Date	Aug. 15, 2047
Senior Notes [Member] | Series due April 1, 2047 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 300	300
Debt Instrument, Interest Rate, Stated Percentage	4.15%
Debt Instrument, Maturity Date	Apr. 1, 2047
Senior Notes [Member] | Series Due April 1, 2030 | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 300	0
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Debt Instrument, Maturity Date	Apr. 1, 2030
Senior Notes [Member] | Series due August 15, 2028 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maturity Date	Aug. 15, 2028
Long-term Debt [Member] | Due August 31, 2062 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 9.4	9.5
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Debt Instrument, Maturity Date	Aug. 31, 2062
Debentures Subject to Mandatory Redemption [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Total long-term debt	$ 135.4
Debentures Subject to Mandatory Redemption [Member] | Garfield Industrial Authority Bond [Member] | Minimum [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.28%
Debentures Subject to Mandatory Redemption [Member] | Garfield Industrial Authority Bond [Member] | Maximum [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.35%
Debentures Subject to Mandatory Redemption [Member] | Garfield Industrial Authority Bond [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 47	47
Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority Bond Due 2025 [Member] | Minimum [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.33%
Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority Bond Due 2025 [Member] | Maximum [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.31%
Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority Bond Due 2025 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 32.4	32.4
Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority Bond Due 2027 [Member] | Minimum [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.28%
Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority Bond Due 2027 [Member] | Maximum [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.35%
Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority Bond Due 2027 [Member] | Og and E [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross	$ 56	$ 56

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	450	450
Common Stock, Shares, Outstanding	200.1	200.1
OG&E [Member]
Common Stock, Par or Stated Value Per Share	$ 2.50	$ 2.50
Common Stock, Shares Authorized	100	100
Common Stock, Shares, Outstanding	40.4	40.4
Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument, Maturity Date	Jan. 1, 2025
Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument, Maturity Date	Jan. 1, 2025
Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument, Maturity Date	Jun. 1, 2027
Senior Notes [Member] | Series Due July 15, 2027 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Jul. 15, 2027
Debt Instrument, Interest Rate, Stated Percentage	6.65%
Senior Notes [Member] | Series Due April 15, 2028 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Apr. 15, 2028
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Senior Notes [Member] | Series Due August 15, 2028 [Member] [Member] | OG&E [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Senior Notes [Member] | Series Due March 15, 2030 | OG&E [Member]
Debt Instrument, Maturity Date	Mar. 15, 2030
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Senior Notes [Member] | Series Due January 15, 2036 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Jan. 15, 2036
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Senior Notes [Member] | Series Due February 1, 2038 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Feb. 1, 2038
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Senior Notes [Member] | Series Due June 1, 2040 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Jun. 1, 2040
Debt Instrument, Interest Rate, Stated Percentage	5.85%
Senior Notes [Member] | Series Due May 15, 2041 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	May 15, 2041
Debt Instrument, Interest Rate, Stated Percentage	5.25%
Senior Notes [Member] | Series Due May 1, 2043 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	May 1, 2043
Debt Instrument, Interest Rate, Stated Percentage	3.90%
Senior Notes [Member] | Series Due March 15, 2044 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Mar. 15, 2044
Debt Instrument, Interest Rate, Stated Percentage	4.55%
Senior Notes [Member] | Series Due December 15, 2044 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Dec. 15, 2044
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Senior Notes [Member] | Series due April 1, 2047 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Apr. 1, 2047
Debt Instrument, Interest Rate, Stated Percentage	4.15%
Senior Notes [Member] | Series due August 15, 2047 [Member] [Domain] | OG&E [Member]
Debt Instrument, Maturity Date	Aug. 15, 2047
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Long-term Debt [Member] | Due August 31, 2062 [Member] | OG&E [Member]
Debt Instrument, Maturity Date	Aug. 31, 2062
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Minimum [Member] | Debentures Subject to Mandatory Redemption [Member] | Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.28%
Minimum [Member] | Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.33%
Minimum [Member] | Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.28%
Maximum [Member] | Debentures Subject to Mandatory Redemption [Member] | Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.35%
Maximum [Member] | Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.31%
Maximum [Member] | Debentures Subject to Mandatory Redemption [Member] | Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.35%

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Premium on Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Common Stock, Shares, Outstanding		199,700
Comprehensive income (loss)
Treasury Stock, Common, Shares						0
Net Income (Loss), Including portion attributable to noncontrolling interest, Number of Shares		0				0
Balance at Dec. 31, 2017	$ 3,851.1	$ 2	$ 1,112.8	$ 2,759.5	$ (23.2)	$ 0
Comprehensive income (loss)
Net income (loss)	425.5	$ 0	0	425.5	0	$ 0
Other Comprehensive Income (Loss), Net of Tax, Number of Shares		0				0
Other Comprehensive Income (Loss), Net of Tax	(5.7)	$ 0	0	0	(5.7)	$ 0
Dividends, Common Stock, Cash, Number of Shares		0				0
Dividends declared on common stock	(278.7)	$ 0	0	(278.7)	0	$ 0
Stock Issued During Period, Shares, New Issues		0				0
Purchase of treasury stock	(0.1)	$ 0	(0.1)	0	0	$ 0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Number of Shares		0				0
Stock-based compensation	13	$ 0	13	0	0	$ 0
Balance at Dec. 31, 2018	$ 4,005.1	$ 2	1,125.7	2,906.3	(28.9)	$ 0
Comprehensive income (loss)
DIVIDENDS DECLARED PER COMMON SHARE	$ 1.3950
Common Stock, Shares, Outstanding		199,700
Treasury Stock, Common, Shares						0
Net Income (Loss), Including portion attributable to noncontrolling interest, Number of Shares		0				0
Net income (loss)	$ 433.6	$ 0	0	433.6	0	$ 0
Other Comprehensive Income (Loss), Net of Tax, Number of Shares		0				0
Other Comprehensive Income (Loss), Net of Tax	1	$ 0	0	0	1	$ 0
Dividends, Common Stock, Cash, Number of Shares		0				0
Dividends declared on common stock	(303.8)	$ 0	0	(303.8)	0	$ 0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Number of Shares		400				0
Stock-based compensation	3.6	$ 0	3.6	0	0	$ 0
Balance at Dec. 31, 2019	$ 4,139.5	$ 2	1,129.3	3,036.1	(27.9)	$ 0
Comprehensive income (loss)
DIVIDENDS DECLARED PER COMMON SHARE	$ 1.5050
Common Stock, Shares, Outstanding	200,100	200,100
Treasury Stock, Common, Shares	0					0
Net Income (Loss), Including portion attributable to noncontrolling interest, Number of Shares		0				0
Net income (loss)	$ (173.7)	$ 0	0	(173.7)	0	$ 0
Other Comprehensive Income (Loss), Net of Tax, Number of Shares		0				0
Other Comprehensive Income (Loss), Net of Tax	(4.2)	$ 0	0	0	(4.2)	$ 0
Dividends, Common Stock, Cash, Number of Shares		0				0
Dividends declared on common stock	(317.8)	$ 0	0	(317.8)	0	$ 0
Treasury Stock, Value, Acquired, Cost Method		$ 0	0	0	0	$ (14.7)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Number of Shares		0				(300)
Stock-based compensation	2.7	$ 0	(6.7)	0	0	$ 9.4
Balance at Dec. 31, 2020	$ 3,631.8	$ 2	$ 1,122.6	$ 2,544.6	$ (32.1)	$ (5.3)
Comprehensive income (loss)
DIVIDENDS DECLARED PER COMMON SHARE	$ 1.5800
Treasury Stock, Shares, Acquired	405	0				400
Common Stock, Shares, Outstanding	200,100	200,100
Treasury Stock, Common, Shares	100					100

STATEMENTS OF CHANGES IN STOCKH

STATEMENTS OF CHANGES IN STOCKHOLDER'S EQUITY - USD ($) shares in Millions, $ in Millions	Total	Og and E [Member]	Common Stock	Common StockOg and E [Member]	Premium on Common Stock	Premium on Common StockOg and E [Member]	Retained Earnings	Retained EarningsOg and E [Member]
Common Stock, Shares, Outstanding			199.7	40.4
Stockholders' Equity Attributable to Parent		$ 3,455.7		$ 100.9		$ 926.3		$ 2,428.5
Net Income (Loss), Including portion attributable to noncontrolling interest, Number of Shares			0	0
Net Income (Loss) Attributable to Parent		328		$ 0		0		328
Dividends, Common Stock, Cash, Number of Shares			0	0
Dividends, Common Stock		(185)		$ 0		0		(185)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Number of Shares			0	0
Stock-based compensation	$ 13	4.6	$ 0	$ 0	$ 13	4.6	$ 0	0
Common Stock, Shares, Outstanding			199.7	40.4
Stockholders' Equity Attributable to Parent		3,603.3		$ 100.9		930.9		2,571.5
Net Income (Loss), Including portion attributable to noncontrolling interest, Number of Shares			0	0
Net Income (Loss) Attributable to Parent		350.2		$ 0		0		350.2
Dividends, Common Stock, Cash, Number of Shares			0
Dividends, Common Stock								0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Number of Shares			0.4	0
Stock-based compensation	$ 3.6	$ (4.8)	$ 0	$ 0	3.6	(4.8)	0	0
Common Stock, Shares, Outstanding	200.1	40.4	200.1	40.4
Stockholders' Equity Attributable to Parent	$ 4,139.5	$ 3,958.3		$ 100.9		935.7		2,921.7
Net Income (Loss), Including portion attributable to noncontrolling interest, Number of Shares			0	0
Net Income (Loss) Attributable to Parent		339.4		$ 0		0		339.4
Dividends, Common Stock, Cash, Number of Shares			0	0
Dividends, Common Stock		(325)		$ 0		0		325
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Number of Shares			0	0
Stock-based compensation	$ 2.7	$ 2.9	$ 0	$ 0	$ (6.7)	2.9	$ 0	0
Common Stock, Shares, Outstanding	200.1	40.4	200.1	40.4
Stockholders' Equity Attributable to Parent	$ 3,631.8	$ 3,975.6		$ 100.9		$ 938.6		$ 2,936.1

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Summary of Significant Accounting Policies Organization OGE Energy is a holding company with investments in energy and energy services providers offering physical delivery and related services for both electricity and natural gas primarily in the south central U.S. OGE Energy conducts these activities through two business segments: (i) electric utility and (ii) natural gas midstream operations. The accounts of OGE Energy and its wholly-owned subsidiaries, including OG&E, are included in OGE Energy's consolidated financial statements. All intercompany transactions and balances are eliminated in such consolidation. OGE Energy generally uses the equity method of accounting for investments where its ownership interest is between 20 percent and 50 percent and it lacks the power to direct activities that most significantly impact economic performance. OG&E . OGE Energy's electric utility operations are conducted through OG&E, which generates, transmits, distributes and sells electric energy in Oklahoma and western Arkansas. OG&E's rates are subject to regulation by the OCC, the APSC and the FERC. OG&E was incorporated in 1902 under the laws of the Oklahoma Territory and is a wholly-owned subsidiary of OGE Energy. OG&E is the largest electric utility in Oklahoma, and its franchised service territory includes Fort Smith, Arkansas and the surrounding communities. OG&E sold its retail natural gas business in 1928 and is no longer engaged in the natural gas distribution business. Enable. OGE Energy's natural gas midstream operations segment represents OGE Energy's investment in Enable. The investment in Enable is held through wholly-owned subsidiaries and ultimately OGE Holdings. Enable is primarily engaged in the business of gathering, processing, transporting and storing natural gas. Enable's natural gas gathering and processing assets are strategically located in four states and serve natural gas production in the Anadarko, Arkoma and Ark-La-Tex Basins. Enable also owns crude oil gathering assets in the Anadarko and Williston Basins. Enable has intrastate natural gas transportation and storage assets that are located in Oklahoma as well as interstate assets that extend from western Oklahoma and the Texas Panhandle to Louisiana, from Louisiana to Illinois and from Louisiana to Alabama. Enable's general partner is equally controlled by OGE Energy and CenterPoint, who each have 50 percent management ownership. Based on the 50/50 management ownership, with neither company having control, OGE Energy accounts for its interest in Enable using the equity method of accounting. In February 2021, Enable entered into a definitive merger agreement with Energy Transfer. For further discussion, see Note 5. OGE Energy charges operating costs to OG&E and Enable based on several factors. Operating costs directly related to OG&E and Enable are assigned as such. Operating costs incurred for the benefit of OG&E and Enable are allocated either as overhead based primarily on labor costs or using the "Distrigas" method. The "Distrigas" method is a three-factor formula that uses an equal weighting of payroll, net operating revenues and gross property, plant and equipment. OGE Energy adopted this method as a result of a recommendation by the OCC Staff. OGE Energy believes this method provides a reasonable basis for allocating common expenses. Use of Estimates In preparing the financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Changes to these assumptions and estimates could have a material effect on the Registrants' financial statements. However, the Registrants believe they have taken reasonable positions where assumptions and estimates are used in order to minimize the negative financial impact to the Registrants that could result if actual results vary from the assumptions and estimates. In management's opinion, the areas where the most significant judgment is exercised include the determination of Pension Plan assumptions, income taxes, contingency reserves, asset retirement obligations, regulatory assets and liabilities, unbilled revenues and the allowance for uncollectible accounts receivable. For OGE Energy, significant judgment is also exercised in the determination of any impairment of equity method investments. Cash and Cash Equivalents For purposes of the financial statements, the Registrants consider all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. These investments are carried at cost, which approximates fair value. Allowance for Uncollectible Accounts Receivable Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is generally calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off and is adjusted for current conditions and supportable forecasts as necessary. To the extent the historical collection rates, when incorporating forecasted conditions, are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized, such as in response to COVID-19 impacts. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the balance sheets and is included in Other Operation and Maintenance Expense in the statements of income. The allowance for uncollectible accounts receivable was $2.6 million and $1.5 million at December 31, 2020 and 2019, respectively. New business customers are required to provide a security deposit in the form of cash, bond or irrevocable letter of credit that is refunded when the account is closed. New residential customers whose outside credit scores indicate an elevated risk are required to provide a security deposit that is refunded based on customer protection rules defined by the OCC and the APSC. The payment behavior of all existing customers is continuously monitored, and, if the payment behavior indicates sufficient risk within the meaning of the applicable utility regulation, customers will be required to provide a security deposit. Investment in Unconsolidated Affiliates OGE Energy's investment in Enable is considered to be a variable interest entity because the owners of the equity at risk in this entity have disproportionate voting rights in relation to their obligations to absorb the entity's expected losses or to receive its expected residual returns. However, OGE Energy is not considered the primary beneficiary of Enable since it does not have the power to direct the activities of Enable that are considered most significant to the economic performance of Enable; therefore, OGE Energy accounts for its investment in Enable using the equity method of accounting. Under the equity method, the investment will be adjusted each period for contributions made, distributions received and OGE Energy's share of the investee's comprehensive income as adjusted for basis differences. OGE Energy's maximum exposure to loss related to Enable is limited to its equity investment in Enable at December 31, 2020 as presented in Note 14. OGE Energy evaluates its equity method investments for impairment when events or changes in circumstances indicate there is a loss in value of the investment that is other than a temporary decline. When indicators exist, the fair value is estimated and compared to the investment carrying value, and if any impairment is judgmentally determined to be other than temporary, the carrying value of the investment is written down to fair value. OGE Energy determined, effective March 31, 2020, that an other than temporary decline in the value of OGE Energy's investment in Enable had occurred. Further information detailing the results of OGE Energy's impairment analysis and fair value measurement can be found in Notes 5 and 7, respectively. OGE Energy considers distributions received from Enable which do not exceed cumulative equity in earnings subsequent to the date of investment to be a return on investment and are classified as operating activities in the statements of cash flows. OGE Energy considers distributions received from Enable in excess of cumulative equity in earnings subsequent to the date of investment to be a return of investment and are classified as investing activities in the statements of cash flows. Allowance for Funds Used During Construction Collection of Sales Tax In the normal course of its operations, OG&E collects sales tax from its customers. OG&E records a current liability for sales taxes when it bills its customers and eliminates this liability when the taxes are remitted to the appropriate governmental authorities. OG&E excludes the sales tax collected from its operating revenues. Revenue Recognition General OG&E recognizes revenue from electric sales when power is delivered to customers. The performance obligation to deliver electricity is generally created and satisfied simultaneously, and the provisions of the regulatory-approved tariff determine the charges OG&E may bill the customer, payment due date and other pertinent rights and obligations of both parties. OG&E measures its customers' metered usage and sends bills to its customers throughout each month. As a result, there is a significant amount of customers' electricity consumption that has not been billed at the end of each month. OG&E accrues an estimate of the revenues for electric sales delivered since the latest billings. Unbilled revenue is presented in Accrued Unbilled Revenues in the balance sheets and in Revenues from Contracts with Customers in the statements of income based on estimates of usage and prices during the period. The estimates that management uses in this calculation could vary from the actual amounts to be paid by customers. Integrated Market and Transmission OG&E currently owns and operates transmission and generation facilities as part of a vertically integrated utility. OG&E is a member of the SPP regional transmission organization and has transferred operational authority, but not ownership, of OG&E's transmission facilities to the SPP. The SPP has implemented FERC-approved regional day-ahead and real-time markets for energy and operating services, as well as associated transmission congestion rights. Collectively, the three markets operate together under the global name, SPP Integrated Marketplace. OG&E represents owned and contracted generation assets and customer load in the SPP Integrated Marketplace for the sole benefit of its customers. OG&E has not participated in the SPP Integrated Marketplace for any speculative trading activities. OG&E records the SPP Integrated Marketplace transactions as sales or purchases per FERC Order 668, which requires that purchases and sales be recorded on a net basis for each settlement period of the SPP Integrated Marketplace. Purchases and sales are based on the fixed transaction price determined by the market at the time of the purchase or sale and the MWh quantity purchased or sold. These results are reported as Revenues from Contracts with Customers or Cost of Sales in the statements of income. OG&E revenues, expenses, assets and liabilities may be adversely affected by changes in the organization, operating and regulation by the FERC or the SPP. OG&E's transmission revenues are generated by the use of OG&E's transmission network by the SPP, which operates the network, on behalf of other transmission owners. OG&E recognizes revenue on the sale of transmission service to its customers over time as the service is provided in the amount OG&E has a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by OG&E's FERC-approved formula transmission rates along with other SPP-specific charges and the megawatt quantity reserved. Other Revenues Other Revenues in the statements of income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC. Income Taxes OGE Energy files consolidated income tax returns in the U.S. federal jurisdiction and various state jurisdictions. OG&E is a part of the consolidated tax return of OGE Energy. Income taxes are generally allocated to each company in the affiliated group, including OG&E, based on its stand-alone taxable income or loss. Federal investment tax credits previously claimed on electric utility property have been deferred and will be amortized to income over the life of the related property. The Registrants use the asset and liability method of accounting for income taxes. Under this method, a deferred tax asset or liability is recognized for the estimated future tax effects attributable to temporary differences between the financial statement basis and the tax basis of assets and liabilities as well as tax credit carry forwards and net operating loss carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period of the change. The Registrants recognize interest related to unrecognized tax benefits in Interest Expense and recognize penalties in Other Expense in the statements of income. Accrued Vacation The Registrants accrue vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Income (Loss) The following table presents changes in the components of accumulated other comprehensive income (loss) attributable to OGE Energy during 2019 and 2020. All amounts below are presented net of tax. Pension Plan and Restoration of Retirement Income Plan Postretirement Benefit Plans (In millions) Net Gain Net Gain (Loss) Prior Service Cost (Credit) Other Comprehensive Loss from Unconsolidated Affiliates Total Balance at December 31, 2018 $ (38.8) $ 4.6 $ 5.3 $ — $ (28.9) Other comprehensive loss before reclassifications (8.3) (0.2) — (0.6) (9.1) Amounts reclassified from accumulated other comprehensive income (loss) 3.4 (0.2) (1.7) — 1.5 Settlement cost 8.6 — — — 8.6 Net current period other comprehensive income (loss) 3.7 (0.4) (1.7) (0.6) 1.0 Balance at December 31, 2019 (35.1) 4.2 3.6 (0.6) (27.9) Other comprehensive income (loss) before reclassifications (5.1) (2.4) — (0.7) (8.2) Amounts reclassified from accumulated other comprehensive income (loss) 3.9 (0.1) (1.7) — 2.1 Curtailment cost — (0.3) — — (0.3) Settlement cost 2.2 — — — 2.2 Net current period other comprehensive income (loss) 1.0 (2.8) (1.7) (0.7) (4.2) Balance at December 31, 2020 $ (34.1) $ 1.4 $ 1.9 $ (1.3) $ (32.1) The following table presents significant amounts reclassified out of accumulated other comprehensive income (loss) by the respective line items in net income (loss) during the years ended December 31, 2020 and 2019. Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in Year Ended December 31, (In millions) 2020 2019 Amortization of Pension Plan and Restoration of Retirement Income Plan items: Actuarial losses $ (5.1) $ (4.5) (A) Settlement cost (2.9) (11.3) (A) (8.0) (15.8) Income (Loss) Before Taxes (1.9) (3.8) Income Tax Expense (Benefit) $ (6.1) $ (12.0) Net Income (Loss) Amortization of postretirement benefit plans items: Prior service credit $ 2.3 $ 2.3 (A) Curtailment cost 0.4 — (A) Actuarial gains 0.1 0.2 (A) 2.8 2.5 Income (Loss) Before Taxes 0.7 0.6 Income Tax Expense (Benefit) $ 2.1 $ 1.9 Net Income (Loss) Total reclassifications for the period, net of tax $ (4.0) $ (10.1) Net Income (Loss) (A) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost (see Note 13 for additional information).
Asset Retirement Obligation Disclosure [Text Block]	OG&E has asset retirement obligations primarily associated with the removal of company-owned wind turbines on leased land, as well as the removal of asbestos from certain power generating stations. OG&E has recorded asset retirement obligations that are being accreted over their respective lives ranging from five to 68 years. Asset retirement obligations are included in Other Deferred Credits in the Registrants' balance sheets. The following table presents changes to OG&E's asset retirement obligations during the years ended December 31, 2020 and 2019. (In millions) 2020 2019 Balance at January 1 $ 73.5 $ 83.9 Accretion expense 0.5 1.0 Revisions in estimated cash flows (A) 5.8 (2.4) Liabilities settled (B) (0.2) (9.0) Balance at December 31 $ 79.6 $ 73.5 (A) Assumptions changed related to the estimated timing and estimated cost of the removal of asbestos at OG&E's generating facilities.
Property, Plant and Equipment Disclosure [Text Block]	Property, Plant and Equipment All property, plant and equipment is recorded at cost. Newly constructed plant is added to plant balances at cost which includes contracted services, direct labor, materials, overhead, transportation costs and the allowance for funds used during construction. Replacements of units of property are capitalized as plant. For assets that belong to a common plant account, the replaced plant is removed from plant balances, and the cost of such property net of any salvage proceeds is charged to Accumulated Depreciation. For assets that do not belong to a common plant account, the replaced plant is removed from plant balances with the related accumulated depreciation, and the remaining balance net of any salvage proceeds is recorded as a loss in the statements of income as Other Expense. Repair and replacement of minor items of property are included in the statements of income as Other Operation and Maintenance Expense. The following tables present OG&E's ownership interest in the jointly-owned McClain Plant and the jointly-owned Redbud Plant, and, as disclosed below, only OG&E's ownership interest is reflected in the property, plant and equipment and accumulated depreciation balances in these tables. The owners of the remaining interests in the McClain Plant and the Redbud Plant are responsible for providing their own financing of capital expenditures. Also, only OG&E's proportionate interests of any direct expenses of the McClain Plant and the Redbud Plant, such as fuel, maintenance expense and other operating expenses, are included in the applicable financial statement captions in the statements of income. December 31, 2020 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 257.1 $ 96.0 $ 161.1 Redbud Plant (A)(B) 51 % $ 531.8 $ 181.9 $ 349.9 (A) Construction work in progress was $0.1 million and $1.8 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $67.3 million. December 31, 2019 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 254.4 $ 83.5 $ 170.9 Redbud Plant (A)(B) 51 % $ 529.9 $ 159.0 $ 370.9 (A) Construction work in progress was $0.2 million and $1.4 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. The following tables present the Registrants' major classes of property, plant and equipment and related accumulated depreciation. December 31, 2020 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment OG&E: Distribution assets $ 4,809.9 $ 1,422.1 $ 3,387.8 Electric generation assets (A) 4,932.2 1,713.6 3,218.6 Transmission assets (B) 2,944.6 591.7 2,352.9 Intangible plant 254.1 153.9 100.2 Other property and equipment 495.3 186.3 309.0 OG&E property, plant and equipment 13,436.1 4,067.6 9,368.5 Non-OG&E property, plant and equipment 6.1 — 6.1 Total OGE Energy property, plant and equipment $ 13,442.2 $ 4,067.6 $ 9,374.6 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $67.3 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.9 million. December 31, 2019 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment OG&E: Distribution assets $ 4,468.6 $ 1,381.1 $ 3,087.5 Electric generation assets (A) 4,838.6 1,601.0 3,237.6 Transmission assets (B) 2,901.1 565.5 2,335.6 Intangible plant 225.2 145.4 79.8 Other property and equipment 473.1 175.1 298.0 OG&E property, plant and equipment 12,906.6 3,868.1 9,038.5 Non-OG&E property, plant and equipment 6.1 — 6.1 Total OGE Energy property, plant and equipment $ 12,912.7 $ 3,868.1 $ 9,044.6 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.8 million. OG&E's unamortized computer software costs, included in intangible plant above, were $89.7 million and $71.3 million at December 31, 2020 and 2019, respectively. OG&E's amortization expense for computer software costs was $14.9 million, $11.0 million and $9.6 million for the years ended December 31, 2020, 2019 and 2018, respectively. Depreciation and Amortization The provision for depreciation, which was 2.6 percent and 2.7 percent of the average depreciable utility plant for 2020 and 2019, respectively, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2021, the provision for depreciation is projected to be 2.6 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2020, 99.0 percent will be amortized over 10.4 years with the remaining 1.0 percent of the intangible plant balance at December 31, 2020 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life, and $3.3 million for certain transmission substation facilities in OG&E's service territory, which is being amortized over a 37 to 59 year period.
Inventory Disclosure [Text Block]	Fuel Inventories Fuel inventories for the generation of electricity consist of coal, natural gas and oil. OG&E uses the weighted-average cost method of accounting for inventory that is physically added to or withdrawn from storage or stockpiles. The amount of fuel inventory was $36.5 million and $46.3 million at December 31, 2020 and 2019, respectively.
Summary of Significant Accounting Policies [Text Block]	Accounting Records The accounting records of OG&E are maintained in accordance with the Uniform System of Accounts prescribed by the FERC and adopted by the OCC and the APSC. Additionally, OG&E, as a regulated utility, is subject to accounting principles for certain types of rate-regulated activities, which provide that certain incurred costs that would otherwise be charged to expense can be deferred as regulatory assets, based on the expected recovery from customers in future rates. Likewise, certain actual or anticipated credits that would otherwise reduce expense can be deferred as regulatory liabilities, based on the expected flowback to customers in future rates. Management's expected recovery of deferred costs and flowback of deferred credits generally results from specific decisions by regulators granting such ratemaking treatment. OG&E records certain incurred costs and obligations as regulatory assets or liabilities if, based on regulatory orders or other available evidence, it is probable that the costs or obligations will be included in amounts allowable for recovery or refund in future rates. The following table presents a summary of OG&E's regulatory assets and liabilities. December 31 (In millions) 2020 2019 REGULATORY ASSETS Current: SPP cost tracker under recovery (A) $ 7.0 $ — Generation Capacity Replacement rider under recovery (A) 4.4 3.7 Fuel clause under recoveries — 39.5 Other (A) 8.4 5.5 Total current regulatory assets $ 19.8 $ 48.7 Non-current: Benefit obligations regulatory asset $ 164.9 $ 167.2 Deferred storm expenses 158.8 65.5 Sooner Dry Scrubbers 19.7 20.6 Pension tracker 18.1 2.3 Smart Grid 11.2 18.4 Unamortized loss on reacquired debt 9.7 10.6 Arkansas deferred pension expenses 9.3 8.0 Frontier Plant deferred expenses 6.4 — COVID-19 impacts 6.4 — Other 11.1 13.4 Total non-current regulatory assets $ 415.6 $ 306.0 REGULATORY LIABILITIES Current: Fuel clause over recoveries $ 28.6 $ 4.8 Oklahoma demand program rider over recovery (B) 1.5 2.0 Reserve for tax refund and interim surcharge (B) 0.8 12.7 SPP cost tracker over recovery (B) — 2.6 Other (B) 4.2 6.9 Total current regulatory liabilities $ 35.1 $ 29.0 Non-current: Income taxes refundable to customers, net $ 867.4 $ 899.2 Accrued removal obligations, net 316.8 318.5 Other 4.7 5.8 Total non-current regulatory liabilities $ 1,188.9 $ 1,223.5 (A) Included in Other Current Assets in the balance sheets. (B) Included in Other Current Liabilities in the balance sheets. OG&E recovers certain SPP costs related to base plan charges from its customers and refunds certain SPP revenues received to its customers in Oklahoma through the SPP cost tracker and in Arkansas through the transmission cost recovery rider. OG&E recovers the Oklahoma jurisdictional portion of costs, including non-fuel operation and maintenance expenses, depreciation, taxes other than income taxes and a return on capital, for its investment in the River Valley plant through the Generation Capacity Replacement Rider. The OCC also authorized OG&E to defer the same costs related to its investment in the Frontier plant to a regulatory asset, and recovery of these costs will be considered in future rate proceedings. Fuel clause under and over recoveries are generated from OG&E's customers when OG&E's cost of fuel either exceeds or is less than the amount billed to its customers, respectively. OG&E's fuel recovery clauses are designed to smooth the impact of fuel price volatility on customers' bills. As a result, OG&E under recovers fuel costs in periods of rising fuel prices above the baseline charge for fuel and over recovers fuel costs when prices decline below the baseline charge for fuel. Provisions in the fuel clauses are intended to allow OG&E to amortize under and over recovery balances. The benefit obligations regulatory asset is comprised of expenses recorded which are probable of future recovery and that have not yet been recognized as components of net periodic benefit cost, including net loss and prior service cost. These expenses are recorded as a regulatory asset as OG&E historically has recovered and currently recovers pension and postretirement benefit plan expense in its electric rates. If, in the future, the regulatory bodies indicate a change in policy related to the recovery of pension and postretirement benefit plan expenses, this could cause the benefit obligations regulatory asset balance to be reclassified to accumulated other comprehensive income. The following table presents a summary of the components of the benefit obligations regulatory asset. December 31 (In millions) 2020 2019 Pension Plan and Restoration of Retirement Income Plan: Net loss $ 147.3 $ 160.5 Postretirement Benefit Plans: Net loss 26.2 23.3 Prior service cost (8.6) (16.6) Total $ 164.9 $ 167.2 OG&E includes in expense any Oklahoma storm-related operation and maintenance expenses up to $2.7 million annually and defers to a regulatory asset any additional expenses incurred over $2.7 million. OG&E expects to recover the amounts deferred each year over a five-year period in accordance with historical practice. As approved by the OCC, OG&E deferred the non-fuel incremental operation and maintenance expenses, depreciation, debt cost associated with the capital investment and related ad valorem taxes for the Dry Scrubbers at Sooner Units 1 and 2 as a regulatory asset, and these costs are being recovered over 25 years. OG&E recovers specific amounts of pension and postretirement medical costs in rates approved in its Oklahoma rate reviews. In accordance with approved orders, OG&E defers the difference between actual pension and postretirement medical expenses and the amount approved in its last Oklahoma rate review as a regulatory asset or regulatory liability. These amounts have been recorded in the Pension tracker regulatory asset in the table above. OG&E deferred to a regulatory asset the incremental and stranded costs that were accumulated during Smart Grid deployment, including (i) costs for web portal access, (ii) costs for education and home energy reports and (iii) stranded costs associated with OG&E's analog electric meters, which have been replaced by smart meters. As approved by the OCC and APSC, these costs are being recovered over a six-year period ending in 2022 in Oklahoma and 2023 in Arkansas. Unamortized loss on reacquired debt is comprised of unamortized debt issuance costs related to the early retirement of OG&E's long-term debt. These amounts are recorded in interest expense and are being amortized over the term of the long-term debt which replaced the previous long-term debt. The unamortized loss on reacquired debt is recovered as a part of OG&E's cost of capital. Arkansas includes a certain level of pension expense in base rates. When the Pension Plan experiences a settlement, which represents an acceleration of future pension costs, OG&E defers to a regulatory asset the Arkansas jurisdictional portion of each settlement, which historically has been recovered from customers over the average life of the remaining plan participants. A portion of these settlements is being recovered in current rates, and recovery of additional amounts will be requested as additional settlements occur. For additional information related to settlements, see Note 13. In response to the COVID-19 pandemic, the OCC and APSC issued orders allowing OG&E to defer certain expenses related to its COVID-19 response. For additional information about these orders, see Note 16 and "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations - Recent Developments." OG&E recovers program costs related to the Demand and Energy Efficiency Program in Oklahoma through the Demand Program Rider, which operates on a three-year program cycle. The current program cycle, which runs through 2021, includes recovery of (i) energy efficiency program costs, (ii) lost revenues associated with certain achieved energy efficiency and demand savings, (iii) performance-based incentives and (iv) costs associated with research and development investments. As a result of filings with the OCC, APSC and FERC, OG&E established mechanisms to refund to customers the amount of excess taxes received through rates, with an ongoing adjustment for any excess accumulated deferred income taxes resulting from the Tax Cuts and Jobs Act of 2017. Additional amounts due to customers will be refunded in accordance with agreements in each jurisdiction. Income taxes refundable to customers, net, represents the reduction in accumulated deferred income taxes resulting from the reduction in the federal income tax rate as part of the Tax Cuts and Jobs Act of 2017 and includes income taxes recoverable from customers that represent income tax benefits previously used to reduce OG&E's revenues (treated as regulatory assets). These liabilities will be returned to customers in varying amounts over approximately 80 years, and the assets will be amortized over the estimated remaining life of the assets to which they relate, as the temporary differences that generated the income tax benefits turn around.
Reclassifications [Text Block]	ReclassificationsCertain prior year amounts have been reclassified to conform to the current year presentation.

Accounting Pronouncements

Accounting Pronouncements	12 Months Ended
	Dec. 31, 2020
Accounting Pronouncement [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Accounting Pronouncements Recently Adopted Accounting Standards The following table presents an overview of recently adopted accounting standards and their impacts on the Registrants. ASU Number and Name Description Date of Adoption Financial Statements and Disclosures Impact ASU 2016-13, "Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Information" This standard requires entities to measure all expected credit losses of financial assets held at a reporting date based on historical experience, current conditions and reasonable and supportable forecasts in order to record credit losses in a more timely manner. January 1, 2020 Utilizing a modified-retrospective approach, the Registrants determined their only financial instrument requiring measurement under ASU 2016-13 is trade receivables. The Registrants consider both future economic conditions and historical data to measure their reserves for trade receivables under this standard and determined no adjustments to their reserves were necessary upon adoption. ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40)" The standard aligns requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. January 1, 2020 The new standard did not have a material effect on the Registrants' financial statements upon adoption. Prospectively, the Registrants record applicable capitalized implementation costs in Other Current Assets in the balance sheets and related amortization expense in Other Operation and Maintenance in the statements of income. ASU 2018-13, "Fair Value Measurement (Topic 820): Disclosure Framework" The standard removes, adds or modifies disclosure requirements that impact all levels of the fair value hierarchy, as well as investments measured using the net asset value practical expedient. January 1, 2020 The Registrants applied the guidance on a retrospective or prospective basis, depending on the requirement, and did not experience a significant impact on their financial statement disclosures. ASU 2018-14, "Compensation - Retirement Benefits - Defined Benefit Plans - General (Subtopic 715-20)" The standard removes, adds or clarifies disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. January 1, 2020 The Registrants applied the guidance on a retrospective basis and did not experience a significant impact on their financial statement disclosures. ASU 2020-04, "Reference Rate Reform (Topic 848)" This standard provides optional expedients and exceptions, if certain criteria are met, for applying GAAP to contracts, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. January 1, 2020 The guidance did not have a material impact upon adoption, nor do the Registrants expect a material impact in the future, on their financial statements. The Registrants believe that other recently adopted and recently issued accounting standards that are not yet effective do not appear to have a material impact on the Registrants' financial position, results of operations or cash flows upon adoption.

Revenue from Contracts with Cus

Revenue from Contracts with Customers (Notes)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	Revenue Recognition The following table presents OG&E's revenues from contracts with customers disaggregated by customer classification. OG&E's operating revenues disaggregated by customer classification can be found in "OG&E (Electric Utility) Results of Operations" within "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations." Year Ended December 31, (In millions) 2020 2019 2018 Residential $ 842.7 $ 865.8 $ 877.8 Commercial 465.6 486.6 500.0 Industrial 192.6 217.8 228.9 Oilfield 169.2 200.4 190.4 Public authorities and street light 172.3 190.3 197.4 System sales revenues 1,842.4 1,960.9 1,994.5 Provision for rate refund 3.8 (0.9) (6.0) Integrated market 49.6 38.4 48.7 Transmission 143.3 148.0 147.4 Other 30.7 29.1 27.1 Revenues from contracts with customers $ 2,069.8 $ 2,175.5 $ 2,211.7

Leases, Codification Topic 842

Leases, Codification Topic 842	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lessee, Operating Leases	Leases Based on their evaluation of all contracts under ASC 842, as described in Note 1, the Registrants concluded they have operating lease obligations for OG&E's railcar leases, testing equipment and wind farm land leases. OGE Energy also has an operating lease obligation for its office space lease. Operating Leases OG&E Railcar Lease Agreement Effective February 1, 2019, OG&E renewed a railcar lease agreement for 780 rotary gondola railcars to transport coal from Wyoming to OG&E's coal-fired generation units. Rental payments are charged to fuel expense and are recovered through OG&E's fuel adjustment clauses. On February 1, 2024, OG&E has the option to either purchase the railcars at a stipulated fair market value or renew the lease. If OG&E chooses not to purchase the railcars or renew the lease agreement and the actual fair value of the railcars is less than the stipulated fair market value, OG&E would be responsible for the difference in those values up to a maximum of $6.8 million. OG&E Testing Equipment Lease Agreement Effective January 1, 2020, OG&E entered into a noncancellable engineering testing equipment lease agreement, with a term of January 1, 2020 to December 31, 2022. OG&E Wind Farm Land Lease Agreements OG&E has operating leases related to land for OG&E's Centennial, OU Spirit and Crossroads wind farms with terms of 25 to 30 years. The Centennial lease has rent escalations which increase annually based on the Consumer Price Index. While lease liabilities are not remeasured as a result of changes to the Consumer Price Index, changes to the Consumer Price Index are treated as variable lease payments and recognized in the period in which the obligation for those payments was incurred. The OU Spirit and Crossroads leases have rent escalations which increase after five and 10 years. Although the leases are cancellable, OG&E is required to make annual lease payments as long as the wind turbines are located on the land. OG&E does not expect to terminate the leases until the wind turbines reach the end of their useful life. OGE Energy Office Space Lease OGE Energy has a noncancellable office space lease agreement, with a term from September 1, 2018 to August 31, 2021, that allows for leasehold improvements. Financial Statement Information and Maturity Analysis of Lease Liabilities OGE Energy's operating lease cost was $6.4 million, $6.0 million and $4.9 million for the years ended December 31, 2020, 2019 and 2018, respectively. OG&E's operating lease cost was $5.5 million, $5.1 million and $4.1 million for the years ended December 31, 2020, 2019 and 2018, respectively. The following table presents amounts recognized for operating leases in the Registrants' cash flow statements and balance sheets and supplemental information related to those amounts recognized. OGE Energy OG&E Year Ended December 31, Year Ended December 31, (In millions) 2020 2019 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 6.4 $ 5.6 $ 5.5 $ 4.8 Right-of-use assets obtained in exchange for new operating lease liabilities $ 1.4 $ 10.7 $ 1.4 $ 10.7 (Dollars in millions) December 31, 2020 December 31, 2019 December 31, 2020 December 31, 2019 Right-of-use assets at period end (A) $ 37.6 $ 40.9 $ 37.0 $ 39.6 Operating lease liabilities at period end (B) $ 42.3 $ 45.8 $ 41.7 $ 44.3 Operating lease weighted-average remaining lease term (in years) 12.5 13.1 12.7 13.5 Operating lease weighted-average discount rate 3.9 % 3.9 % 3.9 % 3.9 % (A) Included in Property, Plant and Equipment in the Registrants' balance sheets. (B) Included in Other Deferred Credits and Other Liabilities in the Registrants' balance sheets. The following table presents a maturity analysis of the Registrants' operating lease liabilities. Future minimum operating lease payments as of December 31: OGE Energy OG&E (In millions) 2021 $ 6.3 $ 5.7 2022 5.7 5.7 2023 5.1 5.1 2024 3.2 3.2 2025 3.0 3.0 Thereafter 31.7 31.7 Total future minimum lease payments 55.0 54.4 Less: Imputed interest 12.7 12.7 Present value of net minimum lease payments $ 42.3 $ 41.7

Investment in Unconsolidated Af

Investment in Unconsolidated Affiliate	12 Months Ended
	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Equity Method Investments and Joint Ventures Disclosure [Text Block]	Investment in Unconsolidated Affiliates In 2013, OGE Energy, CenterPoint and the ArcLight group formed Enable as a private limited partnership, and OGE Energy and the ArcLight group indirectly contributed 100 percent of the equity interests in Enogex LLC to Enable. OGE Energy determined that its contribution of Enogex LLC to Enable met the requirements of being in substance real estate and recorded the contribution at historical cost. The formation of Enable was considered a business combination, and CenterPoint was the acquirer of Enogex Holdings for accounting purposes. Under this method, the fair value of the consideration paid by CenterPoint for Enogex Holdings was allocated to the assets acquired and liabilities assumed based on their fair value. Enogex Holdings' assets, liabilities and equity were accordingly adjusted to estimated fair value, resulting in an increase to Enable's equity of $2.2 billion. Since the contribution of Enogex LLC to Enable was recorded at historical cost, the effects of the amortization and depreciation expense associated with the fair value adjustments on Enable's results of operations have been eliminated in OGE Energy's recording of its equity in earnings of Enable. As prior real estate sales accounting guidance was superseded by ASU 2017-05, "Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets," OGE Energy recognizes gains or losses on sales or dilution events in its investment in Enable within OGE Energy's earnings, net of proportional basis difference recognition. At December 31, 2020, OGE Energy owned 111.0 million common units, or 25.5 percent, of Enable's outstanding common units. On December 31, 2020, Enable's common unit price closed at $5.26. OGE Energy recorded equity in losses of unconsolidated affiliates of $668.0 million for the year ended December 31, 2020 compared to equity in earnings of unconsolidated affiliates of $113.9 million and $152.8 million for the years ended 2019 and 2018, respectively. Equity in earnings (losses) of unconsolidated affiliates includes OGE Energy's share of Enable's earnings adjusted for the amortization of the basis difference of OGE Energy's original investment in Enogex LLC and its underlying equity in the net assets of Enable, as well as any impairment OGE Energy records on its investment in Enable. Equity in earnings (losses) of unconsolidated affiliates is also adjusted for the elimination of the Enogex Holdings fair value adjustments, as described above. These amortizations may also include gain or loss on dilution, net of proportional basis difference recognition. OGE Energy evaluates its equity method investment for impairment when factors indicate that a decline in the value of its investment has occurred and the carrying amount of its investment may not be recoverable. An impairment loss, based on the excess of the carrying value over estimated fair value of the investment, is recognized in earnings when an impairment is deemed to be other than temporary. Considerable judgment is used in determining if an impairment loss is other than temporary and the amount of any impairment. Effective March 31, 2020, OGE Energy estimated the fair value of its investment in Enable was below the book value and concluded the decline in value was not temporary due to the severity of the decline and the recent rapid deterioration, as well as the near term future outlook, of the midstream oil and gas industry. Accordingly, OGE Energy recorded a $780.0 million impairment on its investment in Enable in March 2020, which is included in Equity in Earnings (Losses) of Unconsolidated Affiliates in OGE Energy's 2020 income statement. Further information concerning the fair value method used to measure the impairment on OGE Energy's investment in Enable can be found in Note 7. The following tables present summarized unaudited financial information for 100 percent of Enable as of December 31, 2020 and 2019 and for the years ended December 31, 2020, 2019 and 2018. December 31, Balance Sheet 2020 2019 (In millions) Current assets $ 381 $ 389 Non-current assets $ 11,348 $ 11,877 Current liabilities $ 582 $ 780 Non-current liabilities $ 4,052 $ 4,077 Year Ended December 31, Income Statement 2020 2019 2018 (In millions) Total revenues $ 2,463 $ 2,960 $ 3,431 Cost of natural gas and NGLs $ 965 $ 1,279 $ 1,819 Operating income $ 465 $ 569 $ 648 Net income $ 52 $ 360 $ 485 The following table presents a reconciliation of OGE Energy's equity in earnings (losses) of unconsolidated affiliates for the years ended December 31, 2020, 2019 and 2018. For further discussion of Enable's net income, see "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations - Results of Operations - OGE Holdings (Natural Gas Midstream Operations)." Year Ended December 31, (In millions) 2020 2019 2018 Enable net income $ 52.0 $ 360.0 $ 485.3 OGE Energy's percent ownership at period end 25.5 % 25.5 % 25.6 % OGE Energy's portion of Enable net income $ 13.2 $ 91.8 $ 124.4 Amortization of basis difference and dilution recognition (A) 98.8 22.1 28.4 Impairment of OGE Energy's equity method investment in Enable (780.0) — — Equity in earnings (losses) of unconsolidated affiliates (B) $ (668.0) $ 113.9 $ 152.8 (A) Includes loss on dilution, net of proportional basis difference recognition. (B) 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. The following table presents a reconciliation of the difference between OGE Energy's investment in Enable and its underlying equity in the net assets of Enable (basis difference) from December 31, 2019 to December 31, 2020. The basis difference is being amortized over approximately 30 years. (In millions) Basis difference at December 31, 2019 $ 652.5 Amortization of basis difference (A) (100.2) Impairment of OGE Energy's equity method investment in Enable 780.0 Basis difference at December 31, 2020 $ 1,332.3 (A) Includes proportional basis difference recognition due to dilution. On April 1, 2020, Enable announced a 50 percent reduction to its quarterly distribution in order to strengthen its balance sheet and increase its annualized retained cash flow. See "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations - Recent Developments" for further discussion of OGE Energy's response. On February 12, 2021, Enable announced a quarterly dividend distribution of $0.16525 per unit on its outstanding common units, which is unchanged from the previous quarter. If cash distributions to Enable's unitholders exceed $0.330625 per unit in any quarter, the general partner will receive increasing percentages, up to 50 percent, of the cash Enable distributes in excess of that amount. OGE Energy is entitled to 60 percent of those "incentive distributions." In certain circumstances, the general partner has the right to reset the minimum quarterly distribution and the target distribution levels at which the incentive distributions receive increasing percentages to higher levels based on Enable's cash distributions at the time of the exercise of this reset election. Distributions received from Enable were $91.7 million, $144.0 million and $141.2 million during the years ended December 31, 2020, 2019 and 2018, respectively. On February 16, 2021, Enable entered into a definitive merger agreement with Energy Transfer, pursuant to which, and subject to the conditions of the merger agreement, all outstanding common units of Enable will be acquired by Energy Transfer in an all-equity transaction. Under the terms of the merger agreement, Enable's common unitholders, including OGE Energy, will receive 0.8595 of one common unit representing limited partner interests in Energy Transfer for each common unit of Enable. The transaction is anticipated to close in 2021. The transaction is subject to the receipt of the required approvals from the holders of a majority of Enable's common units, anti-trust approvals and other customary closing conditions. Assuming the transaction closes, OGE Energy will own approximately three percent of Energy Transfer's outstanding limited partner units in lieu of the 25.5 percent interest in Enable that it currently owns.

Related Party Disclosures

Related Party Disclosures	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions Disclosure	Related Party Transactions OGE Energy charges operating costs to OG&E and Enable based on several factors, and operating costs directly related to OG&E and/or Enable are assigned as such. Operating costs incurred for the benefit of OG&E are allocated either as overhead based primarily on labor costs or using the "Distrigas" method, which is a three-factor formula that uses an equal weighting of payroll, net operating revenues and gross property, plant and equipment. OGE Energy and OG&E OGE Energy charged operating costs to OG&E of $140.6 million, $149.8 million and $140.9 million during the years ended December 31, 2020, 2019 and 2018, respectively. In 2020 and 2018, OG&E declared dividends to OGE Energy of $325.0 million and $185.0 million, respectively. In 2019, no dividends were declared from OG&E to OGE Energy. OGE Energy and Enable OGE Energy and Enable are currently parties to several agreements whereby OGE Energy provides specified support services to Enable, such as certain information technology, payroll and benefits administration. Under these agreements, OGE Energy charged operating costs to Enable of $0.4 million, $0.5 million and $0.6 million for December 31, 2020, 2019 and 2018, respectively. Pursuant to a seconding agreement, OGE Energy provides seconded employees to Enable to support Enable's operations. As of December 31, 2020, 76 employees that participate in OGE Energy's defined benefit and retirement plans are seconded to Enable. OGE Energy billed Enable for reimbursement of $17.3 million, $23.2 million and $27.5 million in 2020, 2019 and 2018, respectively, under the seconding agreement for employment costs. If the seconding agreement were terminated, and those employees were no longer employed by OGE Energy, and lump sum payments were made to those employees, OGE Energy would recognize a settlement or curtailment of the pension/retiree health care charges, which would increase expense at OGE Energy by $19.0 million. Settlement and curtailment charges associated with the Enable seconded employees are not reimbursable to OGE Energy by Enable. The seconding agreement can be terminated by mutual agreement of OGE Energy and Enable or solely by OGE Energy upon 120 days' notice. OGE Energy had accounts receivable from Enable for amounts billed for support services, including the cost of seconded employees, of $2.0 million and $0.8 million as of December 31, 2020 and 2019, which are included in Accounts Receivable in OGE Energy's balance sheets. Assuming the pending merger between Enable and Energy Transfer is completed, these agreements between OGE Energy and Enable pursuant to which OGE Energy provides support services and seconded employees will be terminated. OG&E and Enable Enable provides gas transportation services to OG&E pursuant to agreements, which expire in May 2024 and December 2038, that grant Enable the responsibility of delivering natural gas to OG&E's generating facilities and performing an imbalance service. With this imbalance service, in accordance with the cash-out provision of the contract, OG&E purchases gas from Enable when Enable's deliveries exceed OG&E's pipeline receipts. Enable purchases gas from OG&E when OG&E's pipeline receipts exceed Enable's deliveries. Further, an additional gas transportation services contract with Enable became effective in December 2018 related to the project to convert Muskogee Units 4 and 5 from coal to natural gas. The following table presents summarized related party transactions between OG&E and Enable during the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, (In millions) 2020 2019 2018 Operating revenues: Electricity to power electric compression assets $ 15.1 $ 15.9 $ 16.3 Cost of sales: Natural gas transportation services $ 32.8 $ 41.2 $ 37.9 Natural gas purchases (sales) $ 2.7 $ (6.0) $ (3.2)

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The classification of the Registrants' fair value measurements requires judgment regarding the degree to which market data is observable or corroborated by observable market data. GAAP establishes a fair value hierarchy that prioritizes the inputs used to measure fair value based on observable and unobservable data. The hierarchy categorizes the inputs into three levels, with the highest priority given to quoted prices in active markets for identical unrestricted assets or liabilities (Level 1) and the lowest priority given to unobservable inputs (Level 3). Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels defined in the fair value hierarchy are as follows: Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the reporting entity's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). The Registrants had no financial instruments measured at fair value on a recurring basis at December 31, 2020 and 2019. The following table presents the carrying amount and fair value of the Registrants' financial instruments at December 31, 2020 and 2019, as well as the classification level within the fair value hierarchy. 2020 2019 December 31 (In millions) Carrying Amount Fair Carrying Amount Fair Classification Long-term Debt (including Long-term Debt due within one year): OG&E Senior Notes $ 3,349.6 $ 4,182.1 $ 3,050.3 $ 3,500.4 Level 2 OG&E Industrial Authority Bonds $ 135.4 $ 135.4 $ 135.4 $ 135.4 Level 2 Tinker Debt $ 9.4 $ 10.7 $ 9.5 $ 10.0 Level 3 Nonrecurring Fair Value Measurements As further discussed in Note 5, OGE Energy recorded an impairment on its investment in Enable in March 2020. The nonrecurring fair value measurement consisted of calculating a 20-trading day volume weighted average price for Enable's common units through March 31, 2020. This method of valuation was determined to be representative of the fair value of Enable's common units as it incorporated market prices during the period and reduced the impact of volatility that a single day could represent. OGE Energy concluded that this valuation method resulted in a Level 3 nonrecurring fair value measurement.

Stock Based Compensation

Stock Based Compensation	12 Months Ended
	Dec. 31, 2020
Stock-Based Compensation [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	Stock-Based Compensation In 2013, OGE Energy adopted, and its shareholders approved, the Stock Incentive Plan. Under the Stock Incentive Plan, restricted stock, restricted stock units, stock options, stock appreciation rights and performance units may be granted to officers, directors and other key employees of OGE Energy and its subsidiaries, including OG&E. OGE Energy has authorized the issuance of up to 7,400,000 shares under the Stock Incentive Plan. The following table presents the Registrants' pre-tax compensation expense and related income tax benefit for the years ended December 31, 2020, 2019 and 2018 related to performance units and restricted stock units for the Registrants' employees. OGE Energy OG&E Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Performance units: Total shareholder return $ 7.9 $ 8.7 $ 8.2 $ 2.3 $ 3.0 $ 2.8 Earnings per share 1.0 4.3 5.1 0.3 1.5 1.8 Total performance units 8.9 13.0 13.3 2.6 4.5 4.6 Restricted stock units 0.9 0.9 0.1 0.4 0.4 — Total compensation expense $ 9.8 $ 13.9 $ 13.4 $ 3.0 $ 4.9 $ 4.6 Income tax benefit $ 2.5 $ 3.6 $ 3.4 $ 0.8 $ 1.3 $ 1.2 During the year ended December 31, 2020, OGE Energy purchased 405,000 shares of its common stock, and 247,252 of these shares were used during the same period to satisfy payouts of earned performance units and restricted stock unit grants to the Registrants' employees pursuant to OGE Energy's Stock Incentive Plan. OGE Energy intends to use the remaining shares to satisfy payouts of earned performance units and restricted stock unit grants to employees pursuant to its Stock Incentive Plan. The shares were purchased at an average cost of $38.04 and $33.14 per share on the open market during March 2020 and August 2020, respectively. OGE Energy records treasury stock purchases at cost. Treasury stock is presented as a reduction of stockholders' equity in OGE Energy's 2020 balance sheet. During the year ended December 31, 2020, there was an immaterial number of shares of new common stock issued pursuant to OGE Energy's Stock Incentive Plan to satisfy restricted stock unit grants to employees. Performance Units Under the Stock Incentive Plan, OGE Energy has issued performance units which represent the value of one share of OGE Energy's common stock. The performance units provide for accelerated vesting if there is a change in control (as defined in the Stock Incentive Plan). Each performance unit is subject to forfeiture if the recipient terminates employment with OGE Energy or a subsidiary prior to the end of the primarily three-year award cycle for any reason other than death, disability or retirement. In the event of death, disability or retirement, a participant will receive a prorated payment based on such participant's number of full months of service during the award cycle, further adjusted based on the achievement of the performance goals during the award cycle. The Registrants estimate expected forfeitures in accounting for performance unit compensation expense. The performance units granted based on total shareholder return are contingently awarded and will be payable in shares of OGE Energy's common stock subject to the condition that the number of performance units, if any, earned by the employees upon the expiration of a primarily three-year award cycle (i.e., three-year cliff vesting period) is dependent on OGE Energy's total shareholder return ranking relative to a peer group of companies. The performance units granted based on earnings per share are contingently awarded and will be payable in shares of OGE Energy's common stock based on OGE Energy's earnings per share growth over a primarily three-year award cycle (i.e., three-year cliff vesting period) compared to a target set at the time of the grant by the Compensation Committee of OGE Energy's Board of Directors. All of these performance units are classified as equity in the balance sheets. If there is no or only a partial payout for the performance units at the end of the award cycle, the unearned performance units are cancelled. Payout requires approval of the Compensation Committee of OGE Energy's Board of Directors. Payouts, if any, are all made in common stock and are considered made when the payout is approved by the Compensation Committee. Performance Units – Total Shareholder Return The fair value of the performance units based on total shareholder return was estimated on the grant date using a lattice-based valuation model that factors in information, including the expected dividend yield, expected price volatility, risk-free interest rate and the probable outcome of the market condition, over the expected life of the performance units. Compensation expense for the performance units is a fixed amount determined at the grant date fair value and is recognized over the primarily three-year award cycle regardless of whether performance units are awarded at the end of the award cycle. Dividends are accrued on a quarterly basis pending achievement of payout criteria and are included in the fair value calculations. Expected price volatility is based on the historical volatility of OGE Energy's common stock for the past three years and is simulated using the Geometric Brownian Motion process. The risk-free interest rate for the performance unit grants is based on the three-year U.S. Treasury yield curve in effect at the time of the grant. The expected life of the units is based on the non-vested period since inception of the award cycle. There are no post-vesting restrictions related to OGE Energy's performance units based on total shareholder return. The following table presents the number of performance units granted based on total shareholder return and the assumptions used to calculate the grant date fair value of the performance units based on total shareholder return. OGE Energy OG&E 2020 2019 2018 2020 2019 2018 Number of units granted 201,552 208,647 261,916 67,975 68,396 91,940 Fair value of units granted $ 38.03 $ 47.00 $ 36.86 $ 38.03 $ 47.00 $ 36.86 Expected dividend yield 3.5 % 4.0 % 3.6 % 3.5 % 4.0 % 3.6 % Expected price volatility 15.0 % 17.0 % 19.0 % 15.0 % 17.0 % 19.0 % Risk-free interest rate 1.17 % 2.47 % 2.38 % 1.17 % 2.47 % 2.38 % Expected life of units (in years) 2.85 2.86 2.86 2.85 2.86 2.86 Performance Units – Earnings Per Share The fair value of the performance units based on earnings per share is based on grant date fair value which is equivalent to the price of one share of OGE Energy's common stock on the date of grant. The fair value of performance units based on earnings per share varies as the number of performance units that will vest is based on the grant date fair value of the units and the probable outcome of the performance condition. OGE Energy reassesses at each reporting date whether achievement of the performance condition is probable and accrues compensation expense if and when achievement of the performance condition is probable. As a result, the compensation expense recognized for these performance units can vary from period to period. There are no post-vesting restrictions related to OGE Energy's performance units based on earnings per share. In 2019, the Compensation Committee of OGE Energy's Board of Directors voted to grant restricted stock units in lieu of performance units based on earnings per share. For 2018, 87,308 and 30,649 performance units based on earnings per share were granted to OGE Energy and OG&E employees, respectively, and the grant date fair value for such units granted was $31.03. Restricted Stock Units Under the Stock Incentive Plan, OGE Energy has issued restricted stock units to certain existing non-officer employees as well as other executives upon hire to attract and retain individuals to be competitive in the marketplace, and as of the 2019 grant cycle, restricted stock units are granted in lieu of performance units based on earnings per share. The restricted stock units vest primarily in a three-year award cycle (i.e., three-year cliff vesting period). Prior to vesting, each restricted stock unit is subject to forfeiture if the recipient ceases to render substantial services to OGE Energy or a subsidiary. These restricted stock units may not be sold, assigned, transferred or pledged and are subject to a risk of forfeiture. The fair value of the restricted stock units was based on the closing market price of OGE Energy's common stock on the grant date. Compensation expense for the restricted stock units is a fixed amount determined at the grant date fair value and is recognized as services are rendered by employees over a primarily three-year vesting period. Also, for those restricted stock units that vest in one-third annual increments over a three-year cycle, OGE Energy treats its restricted stock units as multiple separate awards by recording compensation expense separately for each tranche whereby a substantial portion of the expense is recognized in the earlier years in the requisite service period. Dividends will only be paid on restricted stock unit awards that vest; therefore, only the present value of dividends expected to vest are included in the fair value calculations. The expected life of the restricted stock units is based on the non-vested period since inception of the primarily three-year award cycle. There are no post-vesting restrictions related to OGE Energy's restricted stock units. The following table presents the number of restricted stock units granted and the grant date fair value. OGE Energy OG&E 2020 2019 2018 2020 2019 2018 Restricted stock units granted 67,193 75,929 826 22,665 26,141 — Fair value of restricted stock units granted $ 43.69 $ 41.71 $ 36.28 $ 43.69 $ 41.63 $ — Performance Units and Restricted Stock Units Activity The following tables present a summary of the activity for the Registrants' performance units and restricted stock units for the year ended December 31, 2020. OGE Energy Performance Units Restricted Total Shareholder Return Earnings Per Share (Dollars in millions) Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Units/shares outstanding at 12/31/19 664,817 155,171 72,880 Granted 201,552 (A) — 67,193 Converted (222,163) (B) $ 11.5 (74,053) (B) $ 6.6 N/A Vested N/A N/A (2,608) $ (0.1) Forfeited (31,944) (2,116) (12,546) Units/shares outstanding at 12/31/20 612,262 $ 5.4 79,002 $ 2.7 124,919 $ 4.0 Units/shares fully vested at 12/31/20 236,990 $ 5.4 79,002 $ 2.7 1,752 $ 0.1 OG&E Performance Units Restricted Total Shareholder Return Earnings Per Share (Dollars in millions) Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Units/shares outstanding at 12/31/19 227,679 53,977 25,005 Granted 67,975 (A) — 22,665 Converted (77,799) (B) $ 4.0 (25,931) (B) $ 2.3 N/A Vested N/A N/A (1,113) $ — Forfeited (28,985) (1,969) (11,100) Employee migration (6,507) (C) (842) (C) (1,327) (C) Units/shares outstanding at 12/31/20 182,363 $ 1.7 25,235 $ 0.8 34,130 $ 1.1 Units/shares fully vested at 12/31/20 75,693 $ 1.7 25,235 $ 0.8 1,114 $ — (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) These amounts represent performance units that vested at December 31, 2019 which were settled in March 2020. (C) Due to certain employees transferring between OG&E and OGE Energy. The following tables present a summary of the activity for the Registrants' non-vested performance units and restricted stock units for the year ended December 31, 2020. OGE Energy Performance Units Restricted Total Shareholder Return Earnings Per Share Number Weighted-Average Number Weighted-Average Number Weighted-Average Units/shares non-vested at 12/31/19 442,654 $ 41.43 81,118 $ 31.03 72,880 $ 41.66 Granted 201,552 (A) $ 38.03 — $ — 67,193 $ 43.69 Vested (236,990) $ 36.86 (79,002) $ 31.03 (2,608) $ 40.30 Forfeited (31,944) $ 41.15 (2,116) $ 31.03 (12,546) $ 42.60 Units/shares non-vested at 12/31/20 375,272 $ 42.51 — $ — 124,919 $ 42.69 OG&E Performance Units Restricted Total Shareholder Return Earnings Per Share Number Weighted-Average Number Weighted-Average Number Weighted-Average Units/shares non-vested at 12/31/19 149,880 $ 41.31 28,046 $ 31.03 25,005 $ 41.62 Granted 67,975 (A) $ 38.03 — $ — 22,665 $ 43.69 Vested (75,693) $ 36.86 (25,235) $ 31.03 (1,113) $ 40.59 Forfeited (28,985) $ 41.12 (1,969) $ 31.03 (11,100) $ 42.60 Employee migration (6,507) (B) $ 40.26 (842) (B) $ 31.03 (1,327) (B) $ 42.76 Units/shares non-vested at 12/31/20 106,670 $ 42.49 — $ — 34,130 $ 42.67 (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) Due to certain employees transferring between OG&E and OGE Energy. Fair Value of Vested Performance Units and Restricted Stock Units The following table presents a summary of the Registrants' fair value for vested performance units and restricted stock units. OGE Energy OG&E Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Performance units: Total shareholder return $ 8.7 $ 9.3 $ 5.9 $ 2.8 $ 3.2 $ 2.1 Earnings per share $ 2.5 $ 5.2 $ 4.9 $ 0.8 $ 0.9 $ 1.7 Restricted stock units $ 0.1 $ 0.1 $ 0.1 $ 0.1 $ — $ — Unrecognized Compensation Cost The following table presents a summary of the Registrants' unrecognized compensation cost for non-vested performance units and restricted stock units and the weighted-average periods over which the compensation cost is expected to be recognized. OGE Energy OG&E December 31, 2020 Unrecognized Compensation Cost (In millions) Weighted Average to be Recognized (In years) Unrecognized Compensation Cost (In millions) Weighted Average to be Recognized (In years) Performance units - total shareholder return $ 7.1 1.62 $ 1.8 1.64 Restricted stock units 1.6 1.65 0.4 1.68 Total unrecognized compensation cost $ 8.7 $ 2.2

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Taxes [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes Income Tax Expense (Benefit) The following table presents the components of income tax expense (benefit). OGE Energy OG&E Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Provision (benefit) for current income taxes: Federal $ 8.4 $ (6.4) $ (1.9) $ (3.8) $ (7.9) $ (12.4) State 0.5 5.1 (4.4) (0.6) 4.1 (4.1) Total provision (benefit) for current income taxes 8.9 (1.3) (6.3) (4.4) (3.8) (16.5) Provision (benefit) for deferred income taxes, net: Federal (105.2) 48.5 74.7 45.7 37.7 53.7 State (31.1) (17.4) 3.7 (6.6) (13.8) 2.7 Total provision (benefit) for deferred income taxes, net (136.3) 31.1 78.4 39.1 23.9 56.4 Deferred federal investment tax credits, net — — 0.1 — — 0.1 Total income tax expense (benefit) $ (127.4) $ 29.8 $ 72.2 $ 34.7 $ 20.1 $ 40.0 OGE Energy files consolidated income tax returns in the U.S. federal jurisdiction and various state jurisdictions. OG&E is a part of the consolidated income tax return of OGE Energy. With few exceptions, the Registrants are no longer subject to U.S. federal tax or state and local examinations by tax authorities for years prior to 2017. Income taxes are generally allocated to each company in the affiliated group, including OG&E, based on its stand-alone taxable income or loss. Federal investment tax credits previously claimed on electric utility property have been deferred and will be amortized to income over the life of the related property. Additionally, OG&E earns federal tax credits associated with production from its wind facilities. Oklahoma production and investment state tax credits are also earned on investments in electric and solar generating facilities which further reduce OG&E's effective tax rate. The following table presents a reconciliation of the statutory tax rates to the effective income tax rate. OGE Energy OG&E Year Ended December 31 2020 2019 2018 2020 2019 2018 Statutory federal tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % Impairment of OGE Energy's investment in Enable (A) 31.6 — — — — — Remeasurement of state deferred tax liabilities 0.9 (0.8) (0.4) — — — Executive compensation limitation 0.2 0.2 0.2 — — — Other 0.1 (0.7) 0.4 0.1 (0.6) (0.1) Federal renewable energy credit (B) (5.0) (6.0) (5.1) (5.4) (7.6) (6.9) Amortization of net unfunded deferred taxes (4.4) (4.5) (2.1) (4.8) (5.6) (2.9) State income taxes, net of federal income tax (1.4) (1.2) 0.4 (1.6) (1.8) (0.2) Stock-based compensation (0.3) (1.2) — — — — 401(k) dividends (0.4) (0.4) (0.3) — — — Federal deferred tax revaluation — — 0.4 — — — Effective income tax rate 42.3 % 6.4 % 14.5 % 9.3 % 5.4 % 10.9 % (A) As further discussed in Note 5, OGE Energy recorded a $780.0 million impairment on its investment in Enable in March 2020, which resulted in a tax benefit being recorded that caused a significant variance to the effective tax rate as compared to the prior year. This variance has been presented in the table as a single line item in order to facilitate comparability of other components of the effective tax rate. (B) Represents credits primarily associated with the production from OG&E's wind farms. The deferred tax provisions are recognized as costs in the ratemaking process by the commissions having jurisdiction over the rates charged by OG&E. The following table presents the components of Deferred Income Taxes at December 31, 2020 and 2019. OGE Energy OG&E December 31 (In millions) 2020 2019 2020 2019 Deferred income tax liabilities, net: Accelerated depreciation and other property related differences $ 1,721.2 $ 1,656.8 $ 1,721.2 $ 1,656.8 Investment in Enable 302.6 478.2 — — Regulatory assets 52.3 28.4 52.3 28.4 Pension Plan 3.9 4.1 27.4 24.5 Bond redemption-unamortized costs 2.0 2.2 2.0 2.2 Derivative instruments 1.7 1.6 — — Federal tax credits (236.6) (238.0) (236.6) (238.0) Income taxes recoverable from customers, net (221.8) (229.9) (221.8) (229.9) State tax credits (204.4) (185.8) (189.0) (170.8) Regulatory liabilities (81.0) (68.1) (81.0) (68.1) Postretirement medical and life insurance benefits (22.4) (23.3) (15.3) (16.0) Asset retirement obligations (20.3) (19.2) (20.3) (19.2) Net operating losses (12.0) (16.6) (1.4) (5.7) Accrued liabilities (9.6) (10.7) (5.2) (4.3) Deferred federal investment tax credits (2.7) (1.8) (2.7) (1.8) Accrued vacation (2.2) (2.1) (1.6) (1.6) Other (1.4) 0.4 (6.5) (4.7) Uncollectible accounts (0.7) (0.4) (0.7) (0.4) Total deferred income tax liabilities, net $ 1,268.6 $ 1,375.8 $ 1,020.8 $ 951.4 As of December 31, 2020, the Registrants have classified $17.6 million of unrecognized tax benefits as a reduction of deferred tax assets recorded. Management is currently unaware of any issues under review that could result in significant additional payments, accruals or other material deviation from this amount. The following table presents a reconciliation of the Registrants' total gross unrecognized tax benefits as of the years ended December 31, 2020, 2019 and 2018. (In millions) 2020 2019 2018 Balance at January 1 $ 20.7 $ 20.7 $ 20.7 Tax positions related to current year: Additions 1.2 — — Balance at December 31 $ 21.9 $ 20.7 $ 20.7 As of December 31, 2020, 2019 and 2018, there were $17.6 million, $16.4 million and $16.4 million, respectively, of unrecognized tax benefits that, if recognized, would affect the annual effective tax rate. Where applicable, the Registrants classify income tax-related interest and penalties as interest expense and other expense, respectively. During the year ended December 31, 2020, there were no income tax-related interest or penalties recorded with regard to uncertain tax positions. The Registrants recognize tax benefits from an uncertain tax position only if it is more likely than not the tax position will be sustained on examination by taxing authorities based on the technical merits of the position. The tax benefits in the financial statements from such positions are then measured based on the largest benefit that has a greater than 50 percent likelihood of being realized on settlement. As a result of those measurements, in September 2020, the Registrants recorded an additional reserve for certain federal research and development credits in the amount of $1.2 million. The Registrants sustained federal and state tax operating losses through 2012 caused primarily by bonus depreciation and other book versus tax temporary differences. Federal net operating losses generated during those years have been fully utilized. State operating losses are being carried forward for utilization in future years. In addition to the tax operating losses, the Registrants were unable to utilize the various tax credits that were generated during those years. These tax losses and credits are being carried as deferred tax assets and will be utilized in future periods. Under current law, the Registrants anticipate future taxable income will be sufficient to utilize remaining losses and credits before they begin to expire after 2020. The following table presents a summary of these carry forwards. OGE Energy OG&E (In millions) Carry Forward Amount Deferred Tax Asset Carry Forward Amount Deferred Tax Asset Earliest Expiration Date State operating loss $ 268.0 $ 12.0 $ 21.5 $ 1.4 2030 Federal tax credits $ 236.6 $ 236.6 $ 236.6 $ 236.6 2032 State tax credits: Oklahoma investment tax credits $ 205.6 $ 162.3 $ 186.1 $ 147.0 N/A Oklahoma capital investment board credits $ 12.7 $ 12.7 $ 12.7 $ 12.7 N/A Oklahoma zero emission tax credits $ 37.2 $ 29.3 $ 37.2 $ 29.3 2021 Louisiana inventory credits $ 0.2 $ 0.1 $ — $ — 2021 N/A - not applicable

Common Equity

Common Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Common Equity	Common Equity OGE Energy Automatic Dividend Reinvestment and Stock Purchase Plan OGE Energy issued no shares of common stock under its Automatic Dividend Reinvestment and Stock Purchase Plan in 2020. OGE Energy may, from time to time, issue shares under its Automatic Dividend Reinvestment and Stock Purchase Plan or purchase shares traded on the open market. At December 31, 2020, there were 4,774,442 shares of unissued common stock reserved for issuance under OGE Energy's Automatic Dividend Reinvestment and Stock Purchase Plan. Earnings (Loss) Per Share Basic earnings (loss) per share is calculated by dividing net income (loss) attributable to OGE Energy by the weighted average number of OGE Energy's common shares outstanding during the period. In the calculation of diluted earnings (loss) per share, weighted average shares outstanding are increased for additional shares that would be outstanding if potentially dilutive securities were converted to common stock. Potentially dilutive securities for OGE Energy consist of performance units and restricted stock units. The following table presents the calculation of basic and diluted earnings (loss) per share for OGE Energy. (In millions except per share data) 2020 2019 2018 Net income (loss) $ (173.7) $ 433.6 $ 425.5 Average common shares outstanding: Basic average common shares outstanding 200.1 200.1 199.7 Effect of dilutive securities: Contingently issuable shares (performance and restricted stock units) — 0.6 0.8 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 Anti-dilutive shares excluded from earnings per share calculation 0.3 — — Dividend Restrictions OGE Energy's Certificate of Incorporation places restrictions on the amount of common stock dividends it can pay when preferred stock is outstanding. Before OGE Energy can pay any dividends on its common stock, the holders of any of its preferred stock that may be outstanding are entitled to receive their dividends at the respective rates as may be provided for the shares of their series. As there is no preferred stock outstanding, that restriction did not place any effective limit on OGE Energy's ability to pay dividends to its shareholders. OGE Energy utilizes receipts from its equity investment in Enable and dividends from OG&E to pay dividends to its shareholders. Enable's partnership agreement requires that it distribute all "available cash," as defined as cash on hand at the end of a quarter after the payment of expenses and the establishment of cash reserves and cash on hand resulting from working capital borrowings made after the end of the quarter. Pursuant to the leverage restriction in OGE Energy's revolving credit agreement, OGE Energy must maintain a percentage of debt to total capitalization at a level that does not exceed 65 percent. The payment of cash dividends indirectly results in an increase in the percentage of debt to total capitalization, which results in the restriction of approximately $815.0 million of OGE Energy's retained earnings from being paid out in dividends. Accordingly, approximately $1.7 billion of OGE Energy's retained earnings as of December 31, 2020 are unrestricted for the payment of dividends. OG&E There were no new shares of OG&E common stock issued in 2020, 2019 or 2018. Dividend Restrictions

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2020
Long-term Debt, Unclassified [Abstract]
Long-Term Debt	Long-Term Debt A summary of the Registrants' long-term debt is included in the statements of capitalization. The Registrants have no long-term debt maturing in the next five years. At December 31, 2020, the Registrants were in compliance with all of their debt agreements. The Registrants have previously incurred costs related to debt refinancing. Unamortized loss on reacquired debt is classified as a Non-Current Regulatory Asset in the balance sheets. Unamortized debt expense and unamortized premium and discount on long-term debt are classified as Long-Term Debt in the balance sheets and are being amortized over the life of the respective debt. OG&E Industrial Authority Bonds OG&E has tax-exempt pollution control bonds with optional redemption provisions that allow the holders to request repayment of the bonds on any business day. The following table presents information about these bonds, which can be tendered at the option of the holder during the next 12 months. Series Date Due Amount (In millions) 0.28% - 5.35% Garfield Industrial Authority, January 1, 2025 $ 47.0 0.33% - 4.31% Muskogee Industrial Authority, January 1, 2025 32.4 0.28% - 5.35% Muskogee Industrial Authority, June 1, 2027 56.0 Total (redeemable during next 12 months) $ 135.4 All of these bonds are subject to an optional tender at the request of the holders, at 100 percent of the principal amount, together with accrued and unpaid interest to the date of purchase. The bond holders, on any business day, can request repayment of the bond by delivering an irrevocable notice to the tender agent stating the principal amount of the bond, payment instructions for the purchase price and the business day the bond is to be purchased. The repayment option may only be exercised by the holder of a bond for the principal amount. When a tender notice has been received by the trustee, a third-party remarketing agent for the bonds will attempt to remarket any bonds tendered for purchase. This process occurs once per week. Since the original issuance of these series of bonds in 1995 and 1997, the remarketing agent has successfully remarketed all tendered bonds. If the remarketing agent is unable to remarket any such bonds, OG&E is obligated to repurchase such unremarketed bonds. As OG&E has both the intent and ability to refinance the bonds on a long-term basis and such ability is supported by an ability to consummate the refinancing, the bonds are classified as Long-Term Debt in the balance sheets. OG&E believes that it has sufficient liquidity to meet these obligations. Issuance of Long-Term Debt In April 2020, OG&E issued $300.0 million of 3.25 percent senior notes due April 1, 2030. The proceeds from the issuance were added to OG&E's general funds to be used for general corporate purposes, including to fund ongoing capital expenditures and working capital.

Short-Term Debt and Credit Faci

Short-Term Debt and Credit Facilities	12 Months Ended
	Dec. 31, 2020
Short-term Debt [Abstract]
Short-Term Debt and Credit Facilities	Short-Term Debt and Credit Facilities The Registrants borrow on a short-term basis, as necessary, by the issuance of commercial paper and by borrowings under their revolving credit agreements. OGE Energy also borrows under term credit agreements maturing in one year or less, as necessary. As of December 31, 2020, OGE Energy had $95.0 million short-term debt as compared to $112.0 million short-term debt at December 31, 2019. At December 31, 2020, OG&E had $272.0 million in advances to OGE Energy compared to $304.8 million at December 31, 2019. In April 2020, OGE Energy entered into a $75.0 million floating rate unsecured one-year term credit agreement and borrowed the full $75.0 million, in order to preserve financial flexibility in response to COVID-19. Advances under this agreement were used to refinance existing indebtedness and for working capital and general corporate purposes of OGE Energy. The term credit agreement contained substantially the same covenants as OGE Energy's existing $450.0 million revolving credit agreement. In September 2020, OGE Energy repaid the $75.0 million borrowed under the term credit agreement. The following table presents information regarding the Registrants' revolving credit agreements at December 31, 2020. Aggregate Amount Weighted-Average Entity Commitment Outstanding (A) Interest Rate Expiration (In millions) OGE Energy (B) $ 450.0 $ 95.0 0.25 % (D) March 8, 2024 (F) OG&E (C)(E) 450.0 0.4 1.00 % (D) March 8, 2024 (F) Total $ 900.0 $ 95.4 0.25 % (A) Includes direct borrowings under the revolving credit agreements, commercial paper borrowings and letters of credit at December 31, 2020. (B) This bank facility is available to back up OGE Energy's commercial paper borrowings and to provide revolving credit borrowings. This bank facility can also be used as a letter of credit facility. (C) This bank facility is available to back up OG&E's commercial paper borrowings and to provide revolving credit borrowings. This bank facility can also be used as a letter of credit facility. (D) Represents the weighted-average interest rate for the outstanding borrowings under the revolving credit agreements, commercial paper borrowings and letters of credit. (E) OG&E has an intercompany borrowing agreement with OGE Energy whereby OG&E has access to up to $350.0 million of OGE Energy's revolving credit amount. This agreement has a termination date of March 8, 2024. At December 31, 2020, there were no intercompany borrowings under this agreement. (F) In March 2017, the Registrants entered into unsecured five-year revolving credit agreements totaling $900.0 million ($450.0 million for OGE Energy and $450.0 million for OG&E). Each of the revolving credit facilities contained an option, which could be exercised up to two times, to extend the term of the respective facility for an additional year. In March 2018, the Registrants each utilized one of those extensions to extend the maturity of their respective credit facility from March 8, 2022 to March 8, 2023. In January 2021, the Registrants each utilized the second of those extensions to extend the maturity of their respective credit facility from March 8, 2023 to March 8, 2024. Commitments of a single existing lender with respect to $50.0 million of OGE Energy's credit facility, however, were not extended and, unless the non-extending lender is replaced in accordance with the terms of the credit facility, such commitments will expire March 8, 2023. The non-extending lender is not party to the OG&E facility. In January 2021, the Registrants each entered into an amendment to their revolving credit facilities which gives each of the Registrants the option of extending such commitments for up to two additional one-year periods. In addition, the amendment addresses the establishment of an alternative rate of interest upon the occurrence of certain events related to the phase out of LIBOR. On February 24, 2021, OGE Energy entered into a commitment letter with Wells Fargo and certain of its affiliates whereby Wells Fargo committed to provide an unsecured term loan facility in the aggregate principal amount of $1.0 billion. While borrowing availability still exists within the Registrants' credit facilities, the $1.0 billion commitment in additional short-term financing is expected to provide additional liquidity to help cover the increased fuel and purchased power costs incurred by OG&E during the February 2021 unprecedented cold weather event. For further discussion, see "Item 9B. Other Information." The Registrants' credit facilities each have a financial covenant requiring that the respective borrower maintain a maximum debt to capitalization ratio of 65 percent, as defined in each such facility. The Registrants' facilities each also contain covenants which restrict the respective borrower and certain of its subsidiaries in respect of, among other things, mergers and consolidations, sales of all or substantially all assets, incurrence of liens and transactions with affiliates. The Registrants' facilities are each subject to acceleration upon the occurrence of any default, including, among others, payment defaults on such facilities, breach of representations, warranties and covenants, acceleration of indebtedness (other than intercompany and non-recourse indebtedness) of $100.0 million or more in the aggregate, change of control (as defined in each such facility), nonpayment of uninsured judgments in excess of $100.0 million and the occurrence of certain Employee Retirement Income Security Act and bankruptcy events, subject where applicable to specified cure periods. The Registrants' ability to access the commercial paper market could be adversely impacted by a credit ratings downgrade or major market disruptions. Pricing grids associated with the Registrants' credit facilities could cause annual fees and borrowing rates to increase if an adverse rating impact occurs. The impact of any future downgrade could include an increase in the costs of the Registrants' short-term borrowings, but a reduction in the Registrants' credit ratings would not result in any defaults or accelerations. Any future downgrade could also lead to higher long-term borrowing costs and, if below investment grade, would require the Registrants to post collateral or letters of credit.

Retirement Plans and Postretire

Retirement Plans and Postretirement Benefit Plans	12 Months Ended
	Dec. 31, 2020
Retirement Plans and Postretirement Benefit Plans [Abstract]
Pension and Other Postretirement Benefits Disclosure [Text Block]	Retirement Plans and Postretirement Benefit Plans OGE Energy sponsors defined benefit pension plans, 401(k) savings plans and other postretirement plans covering certain employees of the Registrants. Pension Plan and Restoration of Retirement Income Plan It is OGE Energy's policy to fund the Pension Plan on a current basis based on the net periodic pension expense as determined by OGE Energy's actuarial consultants. Such contributions are intended to provide not only for benefits attributed to service to date but also for those expected to be earned in the future. OGE Energy made a $20.0 million contribution to its Pension Plan in both 2020 and 2019, of which $10.0 million and $5.0 million was attributed to OG&E in 2020 and 2019, respectively. In January 2021, OGE Energy made a $40.0 million contribution to its Pension Plan and has not determined whether it will need to make any additional contributions to the Pension Plan in 2021. Any contribution to the Pension Plan during 2021 would be a discretionary contribution, anticipated to be in the form of cash, and is not required to satisfy the minimum regulatory funding requirement specified by the Employee Retirement Income Security Act of 1974, as amended. OGE Energy could be required to make additional contributions if the value of its pension trust and postretirement benefit plan trust assets are adversely impacted by a major market disruption in the future. In accordance with ASC Topic 715, "Compensation - Retirement Benefits," a one-time settlement charge is required to be recorded by an organization when lump sum payments or other settlements that relieve the organization from the responsibility for the pension benefit obligation during the plan year exceed the service cost and interest cost components of the organization's net periodic pension cost. During 2020, 2019 and 2018, the Registrants experienced an increase in both the number of employees electing to retire and the amount of lump sum payments paid to such employees upon retirement, which resulted in the Registrants recording pension plan settlement charges as presented in the Pension Plan net periodic benefit cost table. The pension settlement charges did not require a cash outlay by the Registrants and did not increase total pension expense over time, as the charges were an acceleration of costs that otherwise would be recognized as pension expense in future periods. OGE Energy provides a Restoration of Retirement Income Plan to those participants in OGE Energy's Pension Plan whose benefits are subject to certain limitations of the Code. Participants in the Restoration of Retirement Income Plan receive the same benefits that they would have received under OGE Energy's Pension Plan in the absence of limitations imposed by the federal tax laws. The Restoration of Retirement Income Plan is intended to be an unfunded plan. OG&E's employees participate in OGE Energy's Pension Plan and Restoration of Retirement Income Plan. Obligations and Funded Status The details of the funded status of OGE Energy's Pension Plan, the Restoration of Retirement Income Plan and the postretirement benefit plans and the amounts included in the balance sheets for 2020 and 2019 are included in the following tables. These amounts have been recorded in Accrued Benefit Obligations with the offset in Accumulated Other Comprehensive Loss (except OG&E's portion, which is recorded as a regulatory asset as discussed in Note 1) in the balance sheets. The amounts in Accumulated Other Comprehensive Loss and those recorded as a regulatory asset represent a net periodic benefit cost to be recognized in the statements of income in future periods. The benefit obligation for OGE Energy's Pension Plan and the Restoration of Retirement Income Plan represents the projected benefit obligation, while the benefit obligation for the postretirement benefit plans represents the accumulated postretirement benefit obligation. The accumulated postretirement benefit obligation for OGE Energy's Pension Plan and Restoration of Retirement Income Plan differs from the projected benefit obligation in that the former includes no assumption about future compensation levels. OGE Energy OG&E Pension Plan Restoration of Retirement Pension Plan Restoration of Retirement December 31 (In millions) 2020 2019 2020 2019 2020 2019 2020 2019 Change in benefit obligation Beginning obligations $ 616.1 $ 615.9 $ 10.3 $ 9.6 $ 462.0 $ 453.6 $ 6.1 $ 6.0 Service cost 13.2 12.9 0.8 0.5 9.2 9.0 0.1 0.2 Interest cost 17.0 20.7 0.2 0.4 12.6 15.6 0.1 0.2 Plan settlements (42.8) (83.1) (5.3) (1.2) (33.5) (45.6) (4.5) (0.9) Plan amendments — — — 0.3 — — — — Plan curtailments — — 0.2 — — — — — Special termination benefits 7.6 — — — 5.1 — — — Actuarial losses 57.7 64.3 1.6 0.7 41.0 42.1 1.2 0.6 Benefits paid (14.2) (14.6) — — (12.3) (12.7) — — Ending obligations $ 654.6 $ 616.1 $ 7.8 $ 10.3 $ 484.1 $ 462.0 $ 3.0 $ 6.1 Change in plans' assets Beginning fair value $ 530.3 $ 522.8 $ — $ — $ 399.1 $ 387.6 $ — $ — Actual return on plans' assets 77.0 85.2 — — 57.0 64.8 — — Employer contributions 20.0 20.0 5.3 1.2 10.0 5.0 4.5 0.9 Plan settlements (42.8) (83.1) (5.3) (1.2) (33.5) (45.6) (4.5) (0.9) Benefits paid (14.2) (14.6) — — (12.3) (12.7) — — Ending fair value $ 570.3 $ 530.3 $ — $ — $ 420.3 $ 399.1 $ — $ — Funded status at end of year $ (84.3) $ (85.8) $ (7.8) $ (10.3) $ (63.8) $ (62.9) $ (3.0) $ (6.1) Accumulated postretirement benefit obligation $ 610.8 $ 563.3 $ 6.9 $ 8.1 $ 454.7 $ 425.8 $ 2.9 $ 4.8 For the year ended December 31, 2020, Pension Plan actuarial losses were primarily due to movement in the discount rate, special termination benefits due to a voluntary retirement program offered by OGE Energy and more retirements and terminations than expected which are expected to accelerate lump sum payments in 2021. These losses were partially offset by gains from lowering the interest crediting rate and plan mortality assumptions. OGE Energy OG&E Postretirement Benefit Plans Postretirement Benefit Plans December 31 (In millions) 2020 2019 2020 2019 Change in benefit obligation Beginning obligations $ 136.5 $ 135.8 $ 104.7 $ 104.8 Service cost 0.2 0.2 0.2 0.2 Interest cost 4.2 5.6 3.2 4.3 Plan curtailments 4.0 — 3.1 — Participants' contributions 3.3 4.1 2.4 3.0 Actuarial losses 7.3 2.9 4.5 2.2 Benefits paid (11.0) (12.1) (8.6) (9.8) Ending obligations $ 144.5 $ 136.5 $ 109.5 $ 104.7 Change in plans' assets Beginning fair value $ 47.0 $ 45.3 $ 41.9 $ 40.6 Actual return on plans' assets 1.2 4.6 1.1 4.0 Employer contributions 7.1 5.1 5.9 4.1 Participants' contributions 3.3 4.1 2.4 3.0 Benefits paid (11.0) (12.1) (8.6) (9.8) Ending fair value $ 47.6 $ 47.0 $ 42.7 $ 41.9 Funded status at end of year $ (96.9) $ (89.5) $ (66.8) $ (62.8) Special termination benefits and curtailment loss for the year ended December 31, 2020 are related to a voluntary retirement program offered by OGE Energy in the fourth quarter of 2020. A curtailment gain or loss is required when the expected future services or benefits in a benefit plan are significantly reduced or eliminated. Net Periodic Benefit Cost The following tables present the net periodic benefit cost components, before consideration of capitalized amounts, of OGE Energy's Pension Plan, Restoration of Retirement Income Plan and postretirement benefit plans that are included in the financial statements. Service cost is presented within Other Operation and Maintenance, and the remaining net period benefit cost components as listed in the following tables are presented within Other Net Periodic Benefit Income (Expense) in the statements of income. OG&E recovers specific amounts of pension and postretirement medical costs in rates approved in its Oklahoma rate reviews. In accordance with approved orders, OG&E defers the difference between actual pension and postretirement medical expenses and the amount approved in its last Oklahoma rate review as a regulatory asset or regulatory liability. These amounts have been recorded in the Pension tracker in the regulatory assets and liabilities table in Note 1 and within Other Net Periodic Benefit Income (Expense) in the statements of income. OGE Energy OG&E Pension Plan Restoration of Retirement Pension Plan Restoration of Retirement Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 2020 2019 2018 2020 2019 2018 Service cost $ 13.2 $ 12.9 $ 14.9 $ 0.8 $ 0.5 $ 0.4 $ 9.2 $ 9.0 $ 9.8 $ 0.1 $ 0.2 $ 0.2 Interest cost 17.0 20.7 23.8 0.2 0.4 0.3 12.6 15.6 17.6 0.1 0.2 0.2 Expected return on plan assets (37.6) (36.1) (44.1) — — — (27.9) (27.6) (33.1) — — — Amortization of net loss 17.1 17.3 16.2 0.5 0.5 0.7 12.1 12.9 12.1 0.4 0.3 0.5 Plan curtailments — — — 0.2 — — — — — — — — Special termination benefits 7.6 — — — — — 5.1 — — — — — Amortization of unrecognized prior service cost (A) — — — — — 0.1 — — — — — — Settlement cost 14.1 27.6 25.1 2.7 0.5 1.0 11.4 16.4 19.4 2.4 0.5 0.4 Total net periodic benefit cost 31.4 42.4 35.9 4.4 1.9 2.5 22.5 26.3 25.8 3.0 1.2 1.3 Less: Amount paid by unconsolidated affiliates (B) 2.0 2.9 2.5 0.1 0.1 0.1 Plus: Amount allocated from OGE Energy (B) 5.9 4.5 5.7 1.3 0.5 1.2 Net periodic benefit cost $ 29.4 $ 39.5 $ 33.4 $ 4.3 $ 1.8 $ 2.4 $ 28.4 $ 30.8 $ 31.5 $ 4.3 $ 1.7 $ 2.5 (A) Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment. (B) "Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E. In addition to the net periodic benefit cost amounts recognized, as presented in the table above, for the Pension and Restoration of Retirement Income Plans in 2020, 2019 and 2018, the Registrants recognized the following: Year Ended December 31 (In millions) 2020 2019 2018 Decrease of pension expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ (13.8) $ (16.1) $ (14.1) Deferral of pension expense related to pension settlement, curtailment and special termination benefits charges: Oklahoma jurisdiction (A) $ 21.6 $ 17.9 $ 22.1 Arkansas jurisdiction (A) $ 2.0 $ 1.7 $ 2.1 (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1. OGE Energy OG&E Postretirement Benefit Plans Postretirement Benefit Plans Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Service cost $ 0.2 $ 0.2 $ 0.3 $ 0.2 $ 0.2 $ 0.2 Interest cost 4.2 5.6 5.4 3.2 4.3 4.2 Expected return on plan assets (1.8) (1.9) (2.0) (1.7) (1.7) (1.8) Amortization of net loss 2.0 2.0 3.8 2.1 2.1 3.8 Plan curtailments 1.5 — — 1.3 — — Amortization of unrecognized prior service cost (A) (8.4) (8.4) (8.4) (6.1) (6.1) (6.1) Total net periodic benefit cost (2.3) (2.5) (0.9) (1.0) (1.2) 0.3 Less: Amount paid by unconsolidated affiliates (B) (0.7) (0.6) (0.5) Plus: Amount allocated from OGE Energy (B) (0.5) (0.6) (0.7) Net periodic benefit cost $ (1.6) $ (1.9) $ (0.4) $ (1.5) $ (1.8) $ (0.4) (A) Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment. (B) "Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E. In addition to the net periodic benefit income amounts recognized, as presented in the table above, for the postretirement benefit plans in 2020, 2019 and 2018, the Registrants recognized the following: Year Ended December 31 (In millions) 2020 2019 2018 Increase of postretirement expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ 0.2 $ 1.0 $ 4.4 Deferral of postretirement expense related to postretirement plan curtailment charges: Oklahoma jurisdiction (A) $ 1.4 $ — $ — Arkansas jurisdiction (A) $ 0.1 $ — $ — (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1. OGE Energy OG&E (In millions) 2020 2019 2018 2020 2019 2018 Capitalized portion of net periodic pension benefit cost $ 3.8 $ 3.6 $ 3.8 $ 3.1 $ 3.0 $ 3.2 Capitalized portion of net periodic postretirement benefit cost $ 0.2 $ 0.2 $ 0.2 $ 0.1 $ 0.1 $ 0.1 Rate Assumptions Pension Plan and Postretirement Year Ended December 31 2020 2019 2018 2020 2019 2018 Assumptions to determine benefit obligations: Discount rate 2.30 % 3.15 % 4.20 % 2.45 % 3.25 % 4.30 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A N/A Interest crediting rate 3.50 % 4.00 % 4.00 % N/A N/A N/A Assumptions to determine net periodic benefit cost: Discount rate 2.88 % 3.63 % 3.73 % 3.25 % 4.30 % 3.70 % Expected return on plan assets 7.50 % 7.50 % 7.50 % 4.00 % 4.00 % 4.00 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A N/A Interest crediting rate 4.00 % 4.00 % 4.00 % N/A N/A N/A N/A - not applicable The discount rate used to compute the present value of plan liabilities is based generally on rates of high-grade corporate bonds with maturities similar to the average period over which benefits will be paid. The discount rate used to determine net benefit cost for the current year is the same discount rate used to determine the benefit obligation as of the previous year's balance sheet date, unless a plan settlement occurs during the current year that requires an updated discount rate for net periodic cost measurement. For 2020 and 2019, the Pension Plan discount rates used to determine net periodic benefit cost are disclosed on a weighted-average basis. The overall expected rate of return on plan assets assumption is used in determining net periodic benefit cost due to recent returns on OGE Energy's long-term investment portfolio. The rate of return on plan assets assumption is the average long-term rate of earnings expected on the funds currently invested and to be invested for the purpose of providing benefits specified by the Pension Plan or postretirement benefit plans. This assumption is reexamined at least annually and updated as necessary. The rate of return on plan assets assumption reflects a combination of historical return analysis, forward-looking return expectations and the plans' current and expected asset allocation. The assumed health care cost trend rates have a significant effect on the amounts reported for postretirement medical benefit plans. Future health care cost trend rates are assumed to be 6.75 percent in 2021 with the rates trending downward to 4.50 percent by 2030. Pension Plan Pension Plan Investments, Policies and Strategies The Pension Plan assets are held in a trust which follows an investment policy and strategy designed to reduce the funded status volatility of the Plan by utilizing liability driven investing. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The investment policy follows a glide path approach that shifts a higher portfolio weighting to fixed income as the Plan's funded status increases. The following table presents the targeted fixed income and equity allocations at different funded status levels. Projected Benefit Obligation Funded Status Thresholds <90% 95% 100% 105% 110% 115% 120% Fixed income 50% 58% 65% 73% 80% 85% 90% Equity 50% 42% 35% 27% 20% 15% 10% Total 100% 100% 100% 100% 100% 100% 100% Within the portfolio's overall allocation to equities, the funds are allocated according to the guidelines in the following table. Asset Class Target Allocation Minimum Maximum Domestic Large Cap Equity 40% 35% 60% Domestic Mid-Cap Equity 15% 5% 25% Domestic Small-Cap Equity 25% 5% 30% International Equity 20% 10% 30% OGE Energy has retained an investment consultant responsible for the general investment oversight, analysis, monitoring investment guideline compliance and providing quarterly reports to certain of the Registrants' members and OGE Energy's Investment Committee. The various investment managers used by the trust operate within the general operating objectives as established in the investment policy and within the specific guidelines established for each investment manager's respective portfolio. The portfolio is rebalanced at least on an annual basis to bring the asset allocations of various managers in line with the target asset allocation listed above. More frequent rebalancing may occur if there are dramatic price movements in the financial markets which may cause the trust's exposure to any asset class to exceed or fall below the established allowable guidelines. To evaluate the progress of the portfolio, investment performance is reviewed quarterly. It is, however, expected that performance goals will be met over a full market cycle, normally defined as a three- to five-year period. Analysis of performance is within the context of the prevailing investment environment and the advisors' investment style. The goal of the trust is to provide a rate of return consistently from three percent to five percent over the rate of inflation (as measured by the national Consumer Price Index) on a fee adjusted basis over a typical market cycle of no less than three years and no more than five years. Each investment manager is expected to outperform its respective benchmark. The following table presents a list of each asset class utilized with appropriate comparative benchmark(s) each manager is evaluated against and the focus of the asset class. Asset Class Comparative Benchmark(s) Focus of Asset Class Active Duration Fixed Income (A)(B) Bloomberg Barclays Aggregate l Maximize risk-adjusted performance while providing long bond exposure managed according to the manager's forecast on interest rates. l All invested assets must reach at or above Baa3 or BBB- investment grade. l Limited five percent exposure to any single issuer, except the U.S. Government or affiliates. Long Duration Fixed Income (A)(B) Duration blended Barclays Long Government/Credit & Barclays Universal l Maximize risk-adjusted performance. l At least 75 percent of invested assets much reach at or above Baaa3 or BBB- investment grade. l Limited five percent exposure to any single issuer, except the U.S. Government or affiliates. l May invest up to 10 percent of the market value in convertible bonds as long as quality guidelines are met. l May invest up to 15 percent of the market value in private placement, including 144A securities with or without registration rights and allow for futures to be traded in the portfolio. Equity Index (B)(C) Standard & Poor's 500 Index l Focus on replicating the performance of the S&P 500 Index. Mid-Cap Equity (B)(C) Russell Midcap Index l Focus on undervalued stocks expected to earn average return and pay out higher than average dividends. l Invest in companies with market capitalizations lower than average company on public exchanges: l Price/earnings ratio at or near referenced index; l Small dividend yield and return on equity at or near referenced index; and l Earnings per share growth rate at or near referenced index. Small-Cap Equity (B)(C) Russell 2000 Index International Equity (D) Morgan Stanley Capital International ACWI ex-U.S. l Invest in non-dollar denominated equity securities. l Diversify the overall trust investments. (A) Investment grades are by Moody's Investors Service, S&P Global Ratings or Fitch Ratings. (B) The purchase of any of OGE Energy's equity, debt or other securities is prohibited. (C) No more than five percent can be invested in any one stock at the time of purchase and no more than 10 percent after accounting for price appreciation. Options or financial futures may not be purchased unless prior approval from OGE Energy's Investment Committee is received. The purchase of securities on margin, securities lending, private placement purchases and venture capital purchases are prohibited. The aggregate positions in any company may not exceed one percent of the fair market value of its outstanding stock. (D) The manager of this asset class is required to operate under certain restrictions including regional constraints, diversification requirements and percentage of U.S. securities. All securities are freely traded on a recognized stock exchange, and there are no over-the-counter derivatives. The following investment categories are excluded: options (other than traded currency options), commodities, futures (other than currency futures or currency hedging), short sales/margin purchases, private placements, unlisted securities and real estate (but not real estate shares). Pension Plan Investments The following tables present the Pension Plan's investments that are measured at fair value on a recurring basis at December 31, 2020 and 2019. There were no Level 3 investments held by the Pension Plan at December 31, 2020 and 2019. (In millions) December 31, 2020 Level 1 Level 2 Net Asset Value (A) Common stocks $ 252.3 $ 252.3 $ — $ — U.S. Treasury notes and bonds (B) 134.3 134.3 — — Mortgage- and asset-backed securities 29.3 — 29.3 — Corporate fixed income and other securities 116.6 — 116.6 — Commingled fund (C) 25.4 — — 25.4 Foreign government bonds 4.6 — 4.6 — U.S. municipal bonds 1.8 — 1.8 — Money market fund 8.8 — — 8.8 Mutual fund 9.2 9.2 — — Preferred stocks 0.6 0.6 — — U.S. Treasury futures: Cash collateral 0.7 0.7 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 583.7 $ 397.1 $ 152.4 $ 34.2 Receivable from broker for securities sold 0.2 Interest and dividends receivable 2.2 Payable to broker for securities purchased (15.8) Total OGE Energy Pension Plan assets $ 570.3 Pension Plan investments attributable to affiliates (150.0) Total OG&E Pension Plan assets $ 420.3 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. (In millions) December 31, 2019 Level 1 Level 2 Net Asset Value (A) Common stocks $ 202.0 $ 202.0 $ — $ — U.S. Treasury notes and bonds (B) 134.8 134.8 — — Mortgage- and asset-backed securities 45.8 — 45.8 — Corporate fixed income and other securities 130.5 — 130.5 — Commingled fund (C) 23.9 — — 23.9 Foreign government bonds 3.0 — 3.0 — U.S. municipal bonds 1.1 — 1.1 — Money market fund 2.4 — — 2.4 Mutual fund 7.5 7.5 — — Preferred stocks 0.7 0.7 — — Futures: U.S. Treasury futures (receivable) 22.9 — 22.9 — U.S. Treasury futures (payable) (10.9) — (10.9) — Cash collateral 0.6 0.6 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 564.4 $ 345.6 $ 192.5 $ 26.3 Interest and dividends receivable 2.4 Payable to broker for securities purchased (36.5) Total OGE Energy Pension Plan assets $ 530.3 Pension Plan investments attributable to affiliates (131.2) Total OG&E Pension Plan assets $ 399.1 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. As defined in the fair value hierarchy, Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible by the Pension Plan at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the Plan's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). Expected Benefit Payments The following table presents the benefit payments the Registrants expect to pay related to the Pension Plan and Restoration of Retirement Income Plan. These expected benefits are based on the same assumptions used to measure OGE Energy's benefit obligation at the end of the year and include benefits attributable to estimated future employee service. (In millions) OGE Energy OG&E 2021 $ 164.2 $ 123.9 2022 $ 43.3 $ 33.1 2023 $ 42.5 $ 31.9 2024 $ 44.2 $ 32.3 2025 $ 41.1 $ 29.3 After 2025 $ 203.6 $ 141.1 Postretirement Benefit Plans In addition to providing pension benefits, OGE Energy provides certain medical and life insurance benefits for eligible retired members. Regular, full-time, active employees hired prior to February 1, 2000 whose age and years of credited service total or exceed 80 or have attained at least age 55 with 10 or more years of service at the time of retirement are entitled to postretirement medical benefits, while employees hired on or after February 1, 2000 are not entitled to postretirement medical benefits. Eligible retirees must contribute such amount as OGE Energy specifies from time to time toward the cost of coverage for postretirement benefits. The benefits are subject to deductibles, co-payment provisions and other limitations. OG&E charges postretirement benefit costs to expense and includes an annual amount as a component of the cost-of-service in future ratemaking proceedings. OGE Energy's contribution to the medical costs for pre-65 aged eligible retirees are fixed at the 2011 level, and OGE Energy covers future annual medical inflationary cost increases up to five percent. Increases in excess of five percent annually are covered by the pre-65 aged retiree in the form of premium increases. OGE Energy provides Medicare-eligible retirees and their Medicare-eligible spouses an annual fixed contribution to an OGE Energy-sponsored health reimbursement arrangement. Medicare-eligible retirees are able to purchase individual insurance policies supplemental to Medicare through a third-party administrator and use their health reimbursement arrangement funds for reimbursement of medical premiums and other eligible medical expenses. Postretirement Plans Investments The following tables present the postretirement benefit plans' investments that are measured at fair value on a recurring basis at December 31, 2020 and 2019. There were no Level 2 investments held by the postretirement benefit plans at December 31, 2020 and 2019. (In millions) December 31, 2020 Level 1 Level 3 Group retiree medical insurance contract $ 33.4 $ — $ 33.4 Mutual fund 10.8 10.8 — Money market fund 3.4 3.4 — Total OGE Energy plan investments $ 47.6 $ 14.2 $ 33.4 Plan investments attributable to affiliates (4.9) Total OG&E plan investments $ 42.7 (In millions) December 31, 2019 Level 1 Level 3 Group retiree medical insurance contract $ 34.8 $ — $ 34.8 Mutual funds 10.9 10.9 — Money market fund 1.2 1.2 — Total OGE Energy plan investments $ 46.9 $ 12.1 $ 34.8 Plan investments attributable to affiliates (5.0) Total OG&E plan investments $ 41.9 The group retiree medical insurance contract invests in a pool of common stocks, bonds and money market accounts, of which a significant portion is comprised of mortgage-backed securities. The unobservable input included in the valuation of the contract includes the approach for determining the allocation of the postretirement benefit plans' pro-rata share of the total assets in the contract. The following table presents a reconciliation of the postretirement benefit plans' investments that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Year Ended December 31 (In millions) 2020 Group retiree medical insurance contract: Beginning balance $ 34.8 Claims paid (3.7) Investment fees (0.1) Interest income 0.8 Net unrealized gains related to instruments held at the reporting date 0.6 Dividend income 0.6 Realized gains 0.4 Ending balance $ 33.4 Medicare Prescription Drug, Improvement and Modernization Act of 2003 The Medicare Prescription Drug, Improvement and Modernization Act of 2003 expanded coverage for prescription drugs. The following table presents the gross benefit payments the Registrants expect to pay related to the postretirement benefit plans, including prescription drug benefits. (In millions) OGE Energy OG&E 2021 $ 11.9 $ 9.4 2022 $ 11.8 $ 9.3 2023 $ 11.4 $ 8.9 2024 $ 10.0 $ 7.7 2025 $ 9.5 $ 7.3 After 2025 $ 40.9 $ 31.0 Post-Employment Benefit Plan Disabled employees receiving benefits from OGE Energy's Group Long-Term Disability Plan are entitled to continue participating in OGE Energy's Medical Plan along with their dependents. The post-employment benefit obligation represents the actuarial present value of estimated future medical benefits that are attributed to employee service rendered prior to the date as of which such information is presented. The obligation also includes future medical benefits expected to be paid to current employees participating in the Group Long-Term Disability Plan and their dependents, as defined in OGE Energy's Medical Plan. The post-employment benefit obligation is determined by an actuary on a basis similar to the accumulated postretirement benefit obligation. The estimated future medical benefits are projected to grow with expected future medical cost trend rates and are discounted for interest at the discount rate and for the probability that the participant will discontinue receiving benefits from OGE Energy's Group Long-Term Disability Plan due to death, recovery from disability or eligibility for retiree medical benefits. OGE Energy's post-employment benefit obligation was $2.2 million and $2.1 million at December 31, 2020 and 2019, respectively, of which $1.8 million and $1.7 million, respectively, was OG&E's portion of the obligation. 401(k) Plan OGE Energy provides a 401(k) Plan, and each regular full-time employee of OGE Energy or a participating affiliate is eligible to participate in the 401(k) Plan immediately upon hire. All other employees of OGE Energy or a participating affiliate are eligible to become participants in the 401(k) Plan after completing one year of service as defined in the 401(k) Plan. Participants may contribute each pay period any whole percentage between two percent and 19 percent of their compensation, as defined in the 401(k) Plan, for that pay period. Participants who have reached age 50 before the close of a year are allowed to make additional contributions referred to as "Catch-Up Contributions," subject to certain limitations of the Code. Participants may designate, at their discretion, all or any portion of their contributions as: (i) a before-tax contribution under Section 401(k) of the Code subject to the limitations thereof, (ii) a contribution made on a non-Roth after-tax basis or (iii) a Roth contribution. The 401(k) Plan also includes an eligible automatic contribution arrangement and provides for a qualified default investment alternative consistent with the U.S. Department of Labor regulations. Participants may elect, in accordance with the 401(k) Plan procedures, to have their future salary deferral rate to be automatically increased annually on a date and in an amount as specified by the participant in such election. For employees hired or rehired on or after December 1, 2009, OGE Energy contributes to the 401(k) Plan, on behalf of each participant, 200 percent of the participant

Report of Business Segments

Report of Business Segments	12 Months Ended
	Dec. 31, 2020
Segment Reporting Information [Line Items]
Report of Business Segments	Report of Business Segments OGE Energy reports its operations in two business segments: (i) the electric utility segment, which is engaged in the generation, transmission, distribution and sale of electric energy and (ii) natural gas midstream operations segment. Other operations primarily includes the operations of the holding company. Intersegment revenues are recorded at prices comparable to those of unaffiliated customers and are affected by regulatory considerations. The following tables present the results of OGE Energy's business segments for the years ended December 31, 2020, 2019 and 2018. 2020 Electric Utility Natural Gas Midstream Operations Other Eliminations Total (In millions) Operating revenues $ 2,122.3 $ — $ — $ — $ 2,122.3 Cost of sales 644.6 — — — 644.6 Other operation and maintenance 464.4 1.7 (3.3) — 462.8 Depreciation and amortization 391.3 — — — 391.3 Taxes other than income 97.2 0.4 3.8 — 101.4 Operating income (loss) 524.8 (2.1) (0.5) — 522.2 Equity in losses of unconsolidated affiliates (A) — (668.0) — — (668.0) Other income (expense) 4.1 (2.9) 3.6 (1.6) 3.2 Interest expense 154.8 — 5.3 (1.6) 158.5 Income tax expense (benefit) 34.7 (158.0) (4.1) — (127.4) Net income (loss) $ 339.4 $ (515.0) $ 1.9 $ — $ (173.7) Investment in unconsolidated affiliates $ — $ 374.3 $ 23.1 $ — $ 397.4 Total assets $ 10,489.0 $ 378.1 $ 116.4 $ (264.7) $ 10,718.8 Capital expenditures $ 650.5 $ — $ — $ — $ 650.5 (A) In March 2020, OGE Energy recorded a $780.0 million impairment on its investment in Enable, as further discussed in Notes 5 and 7. 2019 Electric Utility Natural Gas Midstream Operations Other Eliminations Total (In millions) Operating revenues $ 2,231.6 $ — $ — $ — $ 2,231.6 Cost of sales 786.9 — — — 786.9 Other operation and maintenance 492.5 2.8 (3.5) — 491.8 Depreciation and amortization 355.0 — — — 355.0 Taxes other than income 89.5 0.4 3.7 — 93.6 Operating income (loss) 507.7 (3.2) (0.2) — 504.3 Equity in earnings of unconsolidated affiliates — 113.9 — — 113.9 Other income (expense) 3.1 (8.6) 2.2 (3.6) (6.9) Interest expense 140.5 — 11.0 (3.6) 147.9 Income tax expense (benefit) 20.1 20.7 (11.0) — 29.8 Net income $ 350.2 $ 81.4 $ 2.0 $ — $ 433.6 Investment in unconsolidated affiliates $ — $ 1,132.9 $ 18.6 $ — $ 1,151.5 Total assets $ 10,076.6 $ 1,135.4 $ 107.0 $ (294.7) $ 11,024.3 Capital expenditures $ 635.5 $ — $ — $ — $ 635.5 2018 Electric Utility Natural Gas Midstream Operations Other Eliminations Total (In millions) Operating revenues $ 2,270.3 $ — $ — $ — $ 2,270.3 Cost of sales 892.5 — — — 892.5 Other operation and maintenance 473.8 1.4 (0.6) — 474.6 Depreciation and amortization 321.6 — — — 321.6 Taxes other than income 88.2 0.6 3.2 — 92.0 Operating income (loss) 494.2 (2.0) (2.6) — 489.6 Equity in earnings of unconsolidated affiliates — 152.8 — — 152.8 Other income (expense) 25.6 (4.9) (3.4) (6.0) 11.3 Interest expense 151.8 — 10.2 (6.0) 156.0 Income tax expense (benefit) 40.0 37.1 (4.9) — 72.2 Net income (loss) $ 328.0 $ 108.8 $ (11.3) $ — $ 425.5 Investment in unconsolidated affiliates $ — $ 1,166.6 $ 10.9 $ — $ 1,177.5 Total assets $ 9,704.5 $ 1,169.8 $ 184.8 $ (310.5) $ 10,748.6 Capital expenditures $ 573.6 $ — $ — $ — $ 573.6

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Public Utility Regulatory Policy Act of 1978 OG&E had QF contracts with AES-Shady Point, Inc. and Oklahoma Cogeneration LLC, which expired in January and August 2019, respectively. For the 320 MW AES-Shady Point, Inc. QF contract and the 120 MW Oklahoma Cogeneration LLC QF contract, OG&E purchased 100 percent of the electricity generated by the qualified cogeneration facilities. In 2019, OG&E received approval from the OCC and APSC to acquire the plants from AES-Shady Point, Inc. and Oklahoma Cogeneration LLC. For the years ended December 31, 2019 and 2018, OG&E made total payments to cogenerators of $14.7 million and $112.4 million, respectively, of which $7.4 million and $60.0 million, respectively, represented capacity payments. All payments for purchased power, including cogeneration, are included in the Registrants' statements of income as Cost of Sales. Purchase Obligations and Commitments The following table presents the Registrants' future purchase obligations and commitments estimated for the next five years. (In millions) 2021 2022 2023 2024 2025 Total Purchase obligations and commitments: Minimum purchase commitments $ 72.5 $ 50.4 $ 50.4 $ 36.7 $ 25.9 $ 235.9 Expected wind purchase commitments 55.2 55.6 56.0 56.6 56.9 280.3 Long-term service agreement commitments 2.4 2.4 7.9 35.1 31.2 79.0 Total purchase obligations and commitments $ 130.1 $ 108.4 $ 114.3 $ 128.4 $ 114.0 $ 595.2 OG&E Minimum Purchase Commitments OG&E has coal contracts for purchases through June 30, 2021, whereby OG&E has the right but not the obligation to purchase a defined quantity of coal. OG&E may also purchase coal through spot purchases on an as-needed basis. As a participant in the SPP Integrated Marketplace, OG&E purchases its natural gas supply through short-term agreements. OG&E relies on a combination of natural gas base load agreements and call agreements, whereby OG&E has the right but not the obligation to purchase a defined quantity of natural gas, combined with day and intra-day purchases to meet the demands of the SPP Integrated Marketplace. OG&E has natural gas transportation service contracts with Enable, ONEOK, Inc. and Southern Star. The contracts with Enable end in May 2024 and December 2038; the contracts with ONEOK, Inc. end in March 2024 and August 2037; and the contract with Southern Star ends in June 2024. These transportation contracts grant Enable, ONEOK, Inc. and Southern Star the responsibility of delivering natural gas to OG&E's generating facilities. OG&E Wind Purchase Commitments The following table presents OG&E's wind power purchase contracts. Company Location Original Term of Contract Expiration of Contract MWs CPV Keenan Woodward County, OK 20 years 2030 152.0 Edison Mission Energy Dewey County, OK 20 years 2031 130.0 NextEra Energy Blackwell, OK 20 years 2032 60.0 The following table presents a summary of OG&E's wind power purchases for the years ended December 31, 2020, 2019 and 2018. Year Ended December 31 (In millions) 2020 2019 2018 CPV Keenan $ 27.5 $ 27.2 $ 27.0 Edison Mission Energy 22.8 23.1 21.7 NextEra Energy 7.0 7.4 6.8 FPL Energy (A) — — 2.1 Total wind power purchased $ 57.3 $ 57.7 $ 57.6 (A) OG&E's purchased power contract with FPL Energy for 50 MWs expired in 2018. OG&E Long-Term Service Agreement Commitments OG&E has a long-term parts and service maintenance contract for the upkeep of the McClain Plant. In May 2013, a new contract was signed that is expected to run for the earlier of 128,000 factored-fired hours or 4,800 factored-fired starts. In December 2015, the McClain Long-Term Service Agreement was amended to define the terms and conditions for the exchange of spare rotors between OG&E and General Electric International, Inc. Based on historical usage and current expectations for future usage, this contract is expected to run until 2033. The contract requires payments based on both a fixed and variable cost component, depending on how much the McClain Plant is used. OG&E has a long-term parts and service maintenance contract for the upkeep of the Redbud Plant. In March 2013, the contract was amended to extend the contract coverage for an additional 24,000 factored-fired hours resulting in a maximum of the earlier of 144,000 factored-fired hours or 4,500 factored-fired starts. Based on historical usage and current expectations for future usage, this contract is expected to run until 2030. The contract requires payments based on both a fixed and variable cost component, depending on how much the Redbud Plant is used. Environmental Laws and Regulations The activities of the Registrants are subject to numerous stringent and complex federal, state and local laws and regulations governing environmental protection. These laws and regulations can change, restrict or otherwise impact the Registrants' business activities in many ways, including the handling or disposal of waste material, planning for future construction activities to avoid or mitigate harm to threatened or endangered species and requiring the installation and operation of emissions or pollution control equipment. Failure to comply with these laws and regulations could result in the assessment of administrative, civil and criminal penalties, the imposition of remedial requirements and the issuance of orders enjoining future operations. Management believes that all of the Registrants' operations are in substantial compliance with current federal, state and local environmental standards. Environmental regulation can increase the cost of planning, design, initial installation and operation of OG&E's facilities. Management continues to evaluate its compliance with existing and proposed environmental legislation and regulations and implement appropriate environmental programs in a competitive market. CO 2 Emission Limits for Existing Generating Units On January 19, 2021, the U.S. Court of Appeals vacated the EPA's latest effort to adopt CO 2 emissions standards for existing coal-fired electric generating units, and the court remanded the matter to the EPA for further consideration. The decision was based on the court's conclusion that the Clean Air Act does not require the EPA to limit the standards to measures that can be applied at and to an existing unit. The time for seeking further judicial review of the decision does not expire until June 18, 2021, and the EPA has not announced how it plans to respond to the decision. The ultimate timing and impact of these standards on OG&E's operations cannot be determined with certainty at this time, although a requirement for significant reduction of CO 2 emissions from existing fossil-fuel-fired power plants ultimately could result in significant additional compliance costs that would affect the Registrants' future financial position, results of operations and cash flows if such costs are not recovered through regulated rates. Other

Rate Matters and Regulation

Rate Matters and Regulation	12 Months Ended
	Dec. 31, 2020
Regulated Operations [Abstract]
Rate Matters and Regulation	Rate Matters and Regulation Regulation and Rates OG&E's retail electric tariffs are regulated by the OCC in Oklahoma and by the APSC in Arkansas. The issuance of certain securities by OG&E is also regulated by the OCC and the APSC. OG&E's transmission activities, short-term borrowing authorization and accounting practices are subject to the jurisdiction of the FERC. The Secretary of the U.S. Department of Energy has jurisdiction over some of OG&E's facilities and operations. In 2020, 86 percent of OG&E's electric revenue was subject to the jurisdiction of the OCC, eight percent to the APSC and six percent to the FERC. The OCC and the APSC require that, among other things, (i) OGE Energy permits the OCC and the APSC access to the books and records of OGE Energy and its affiliates relating to transactions with OG&E; (ii) OGE Energy employ accounting and other procedures and controls to protect against subsidization of non-utility activities by OG&E's customers; and (iii) OGE Energy refrain from pledging OG&E assets or income for affiliate transactions. In addition, the FERC has access to the books and records of OGE Energy and its affiliates as the FERC deems relevant to costs incurred by OG&E or necessary or appropriate for the protection of utility customers with respect to the FERC jurisdictional rates. Completed Regulatory Matters APSC Proceedings Arkansas 2019 Formula Rate Plan Filing OG&E filed its second evaluation report under its Formula Rate Plan in October 2019. On February 28, 2020, the APSC approved a settlement agreement among OG&E, the General Staff of the APSC and the Office of the Arkansas Attorney General providing for a $5.2 million revenue increase, with rates effective April 1, 2020. The settling parties agreed that the Series I grid modernization projects are prudent in both action and cost and that the Series II grid modernization projects are prudent in action only and the determination of prudence of costs will be reserved until the actual historical costs are reviewed. The settling parties also agreed that OG&E will no longer use projections for the remaining initial term or extension of its current Formula Rate Plan and that all costs will be included for recovery for the first time in the historical year. Order Regarding COVID-19 On April 10, 2020, the APSC issued Order No. 1 related to COVID-19 and the provision of safe, adequate and reliable utility service at just and reasonable rates. Among other things, the APSC ordered the suspension of customer disconnects for non-payment during the pendency of the Arkansas Governor's emergency declaration or until the directive is rescinded by the APSC, neither of which have occurred yet, although the APSC has requested comments as to whether the moratorium should be lifted. The order encourages companies to provide reasonable payment arrangements once the suspension is lifted. The APSC also authorized utilities to establish regulatory assets to record costs resulting from the suspension of disconnections. These regulatory assets will be reviewed in future proceedings for reasonableness. The APSC ordered the General Staff of the APSC to consult with utilities to create a quarterly report to be used to report the costs incurred and saved that have been booked to the regulatory asset. OG&E is monitoring the regulatory activity regarding COVID-19 at the APSC and will consider the request for additional regulatory action by the APSC as needed. On May 1, 2020, OG&E filed a Request for Additional Actions and Tariff Deviation seeking relief from the Arkansas General Service Rules and OG&E's Terms and Conditions under the tariff, in order to allow for: more flexible deferred payment agreements for all customer classes, suspension of increased deposits due to non-payment and suspension of the removal of customers from certain billing and extended due date plans for late payments. In addition, OG&E requested that incremental expenses, such as additional personal protective equipment, increased sanitation efforts at facilities, implementing health-screening processes and securing temporary facilities for potential sequestration of critical operation personnel, be tracked in a regulatory asset. OG&E noted that all possible cost categories are not known currently and reserved the right to file subsequent requests as needed. On May 27, 2020, the APSC issued an order approving OG&E's request to deviate from the specified terms in the Arkansas General Service Rules and OG&E's Terms and Conditions to allow deferred payment arrangements to be offered to all customer classes and have more flexible payment arrangements. OG&E is authorized to record the expenses requested in its regulatory asset to defer and seek future recovery. The APSC found that because each utility has different cost recovery mechanisms and the magnitude of the utilities' expenses are unknown at this time, the APSC finds that it is premature to decide the exact recovery mechanism for any utility for COVID-19 related costs. Environmental Compliance Plan Rider In May 2019, OG&E filed an environmental compliance plan rider in Arkansas to recover its investment for the environmentally mandated costs associated with the Sooner Dry Scrubbers project and the conversion of Muskogee Units 4 and 5 to natural gas. The filing initiated an interim surcharge, subject to refund, that began with the first billing cycle of June 2019. OG&E had been reserving the amounts collected through the interim surcharge, pending APSC approval of OG&E's filing. A hearing on the merits was held in December 2019. Parties submitted additional briefs to the APSC in March 2020, which were requested due to certain intervenors questioning whether a company can utilize an environmental compliance plan rider while also being regulated under a formula rate plan. The APSC Staff concurred with OG&E that the rider may run concurrently with a formula rate plan, and the Arkansas Attorney General and other intervenors were in opposition. On July 31, 2020, OG&E's request to recover its investment for these environmentally mandated costs through the interim surcharge was not approved, as the APSC indicated OG&E could otherwise recover this investment, such as through the Formula Rate Plan Rider. As of December 31, 2020, OG&E has returned $5.3 million to customers that had been reserved for refund and has included those costs for recovery in its 2020 Formula Rate Plan filing. Arkansas Solar On July 29, 2020, OG&E submitted its application for a Certificate of Public Convenience and Necessity to construct and operate a five MW solar generation facility near Branch, Arkansas. On September 30, 2020, the parties reached a unanimous settlement agreement relating to the filing, and on November 6, 2020, the APSC issued a final order approving the settlement agreement. The terms of the settlement are as follows: (i) parties agree that OG&E has complied with Arkansas law and rules of practice and procedure and recommend granting a Certificate of Public Convenience and Necessity for the construction, ownership and operation of the project and associated tariffs; (ii) OG&E agrees that it would not seek cost recovery until its next general rate review or Formula Rate Plan filing; (iii) OG&E agrees to keep detailed records of final cost, for review at such time that cost recovery is sought, including all cost variance estimates, whereby a determination of prudency of cost may be made; and (iv) OG&E agrees to reserve 50 percent of the total expected energy produced for residential customers for the first 90 days of the program's initial subscription period. Net Metering Order On June 1, 2020, the APSC revised its net-metering rules. The revised rules retained 1:1 full credit for net excess generation of residential customers and commercial customers up to 1 MW without demand charges. For larger commercial customers, 1 MW to 20 MW, the APSC found that some cost shifting to non-net-metering customers may occur. While the rules retain 1:1 full credit for net excess generation, they allow for a grid charge. The grid charge is initially set at zero; however, a utility may request approval to revise the grid charge based on evidence that an unreasonable cost shift to non-net-metering customers is occurring. OG&E does not currently have a significant number of net-metering customers in Arkansas. OG&E amended its existing net-metering tariffs considering the new rules. The APSC approved OG&E's revised tariffs on February 5, 2021. OCC Proceedings OCC Public Utility Division Motion Regarding COVID-19 On April 28, 2020, the Director of the Public Utility Division filed an application requesting an order from the OCC authorizing action in response to COVID-19. The application requested that the OCC authorize the State's utilities to record as a regulatory asset increased bad debt expenses, costs associated with expanded payment plans, waived fees and incremental expenses that are directly related to the suspension of or delay in disconnection of service beginning March 15, 2020, which coincides with the issuance of the Oklahoma Governor's emergency declaration. The application also requested that the OCC allow utilities to defer additional expenses associated with ensuring the continuity of utility service, such as additional personal protective equipment, increased sanitation efforts at facilities, implementing heath-screening processes and securing temporary facilities for potential sequestration of critical operation personnel. The application asked the OCC to consider in future proceedings whether each utility's request for recovery of these regulatory assets is reasonable and necessary and to consider issues such as the incremental bad debt experienced over normal periods, the appropriate period of recovery for any approved amount of regulatory asset, any amount of carrying costs and other related matters. On May 7, 2020, the OCC ordered that each utility is authorized to record as a regulatory asset any increased bad debt expense, cost associated with expanded payment plans, waived fees and incremental expenses that are directly related to the suspension of or delay in disconnection of service beginning March 15, 2020 until September 2020, unless otherwise ordered by the OCC. The OCC will consider in future proceedings whether each utility's request for recovery of these regulatory assets is reasonable and necessary. The OCC will also consider issues such as the incremental bad debt experienced over normal periods, appropriate period of recovery for any approved amount of regulatory assets, any amounts of carrying costs thereon and other related matters. The OCC also authorized utilities to defer expenses associated with ensuring continuity of service and protecting utility personnel, customers and the general public. 2019 Oklahoma Fuel Prudency On June 16, 2020, the Public Utility Division Staff filed their application initiating the review of the 2019 fuel adjustment clause and prudence review. On December 30, 2020, the OCC issued a final order finding OG&E's 2019 fuel costs and related practices prudent. Oklahoma Grid Enhancement Plan On February 24, 2020, OG&E filed an application with the OCC for approval of a mechanism that allows for interim recovery of the costs associated with its grid enhancement plan. The plan includes approximately $800.0 million of strategic, data-driven investments, over five years, covering grid resiliency, grid automation, communication systems and technology platforms and applications. On May 19, 2020, the OCC temporarily suspended the procedural schedule in light of various conditions related to the COVID-19 pandemic and the uncertainty surrounding the method and date in which the hearing on the merits may occur. On July 9, 2020, a prehearing conference was held before the Administrative Law Judge to establish a procedural schedule and lift the stay ordered on May 19, 2020. On July 23, 2020, the OCC issued an order approving the amended procedural schedule and thereby lifting the stay. On October 5, 2020, OG&E filed a Joint Stipulation and Settlement Agreement that included the following key terms: (i) cost recovery through a rider mechanism will be limited to projects placed in service in 2020 and 2021, capped at a revenue requirement of $7.0 million annually and only include communication, automation and technology systems projects; (ii) no operation and maintenance expense will be included in the rider mechanism; (iii) the rider mechanism will terminate by the issuance of a final order in OG&E's next general rate review or October 31, 2022, whichever occurs first; (iv) the rider mechanism rate of return will be capped at OG&E's current cost of capital; and (v) all cost recovery is subject to true-up and refund in OG&E's next general rate review. On November 5, 2020, the OCC issued a final order approving the Joint Stipulation and Settlement Agreement. In compliance with the final order, OG&E submitted a final list of projects for inclusion in the rider mechanism on December 5, 2020 and a revised rider mechanism for initial recovery of costs on December 15, 2020. The rider mechanism became effective on February 1, 2021. Any capital investment falling outside the criteria of the rider mechanism will be included in OG&E's next general rate review for recovery. Pending Regulatory Matters Various proceedings pending before state or federal regulatory agencies are described below. Unless stated otherwise, the Registrants cannot predict when the regulatory agency will act or what action the regulatory agency will take. The Registrants' financial results are dependent in part on timely and adequate decisions by the regulatory agencies that set OG&E's rates. FERC Proceedings Order for Sponsored Transmission Upgrades within SPP Under the SPP Open Access Transmission Tariff, costs of participant-funded, or "sponsored," transmission upgrades may be recovered from other SPP customers whose transmission service depends on capacity enabled by the upgrade. The SPP Open Access Transmission Tariff required the SPP to charge for these upgrades beginning in 2008, but the SPP had not been charging its customers for these upgrades due to information system limitations. However, the SPP had informed participants in the market that these charges would be forthcoming. In July 2016, the FERC granted the SPP's request to recover the charges not billed since 2008. The SPP subsequently billed OG&E for these charges and credited OG&E related to transmission upgrades that OG&E had sponsored, which resulted in OG&E being a net receiver of sponsored upgrade credits. The majority of these net credits were refunded to customers through OG&E's various rate riders that include SPP activity with the remaining amounts retained by OG&E. Several companies that were net payers of Z2 charges sought rehearing of the FERC's July 2016 order; however, in November 2017, the FERC denied the rehearing requests. In January 2018, one of the impacted companies appealed the FERC's decision to the U.S. Court of Appeals for the District of Columbia Circuit. In July 2018, that court granted a motion requested by the FERC that the case be remanded back to the FERC for further examination and proceedings. In February 2019, the FERC reversed its July 2016 order and November 2017 rehearing denial, ruled that the SPP violated its tariff to charge for the 2008 - 2015 period in 2016, held that the SPP tariff provision that prohibited those charges could not be waived and ordered the SPP to develop a plan to refund the payments but not to implement the refunds until further ordered to do so. In response, in April 2019, OG&E filed a request for rehearing with the FERC, and in May 2019, OG&E filed a FERC 206 complaint against the SPP, alleging that the SPP's forced unwinding of the revenue credit payments to OG&E would violate the provisions of the Sponsored Upgrade Agreement and of the applicable tariff. OG&E's filing requested that the FERC rule that the SPP is not entitled to seek refunds or in any other way seek to unwind the revenue credit payments it had paid to OG&E pursuant to the Sponsored Upgrade Agreement. The SPP's response to OG&E's filing agreed that OG&E should be entitled to keep its Z2 payments and argued that the SPP should not be held responsible for those payments if refunds are ordered. Further, the SPP has requested the FERC to negotiate a global settlement with all impacted parties, including other project sponsors who, like OG&E, have also filed complaints at FERC contending that the payments they have received cannot properly be unwound. On February 20, 2020, the FERC denied OG&E's request for rehearing of its February 2019 order, denying the waiver and ruling that the SPP must seek refunds from project sponsors for Z2 payments for the 2008 through 2015 period and pay them back to transmission owners. The FERC also denied the SPP's request for a stay and for institution of settlement procedures. The FERC stated it would not institute settlement procedures unless parties on both sides of the matter requested them. The FERC did not rule on OG&E's complaint or the complaints of other project sponsors, or consider the SPP's refund plan. The FERC thus has not set any date for payment of refunds. On March 2, 2020, OG&E petitioned the U.S. Court of Appeals for the District of Columbia Circuit for review of the FERC's order denying the waiver and requiring refunds. The appeal will likely be decided by the second quarter of 2021. The Registrants cannot predict the outcome of this proceeding based on currently available information, and as of December 31, 2020 and at present time, the Registrants have not reserved an amount for a potential refund. If the reversal of the July 2016 FERC order remains intact, OG&E estimates it would be required to refund $13.0 million, which is net of amounts paid to other utilities for upgrades and would be subject to interest at the FERC-approved rate. If refunds were required, recovery of these upgrade credits would shift to future periods. Of the $13.0 million, the Registrants would be impacted by $5.0 million in expense that initially benefited the Registrants in 2016, and OG&E customers would incur a net impact of $8.0 million in expense through rider mechanisms or the FERC formula rate. On January 31, 2020, the FERC acted on an SPP proposal to eliminate Attachment Z2 revenue crediting and replace it with a different rate mechanism that would provide project sponsors, such as OG&E, the same level of recovery, and rejected the proposal to the extent it would limit recovery to the amount of the upgrade sponsor's directly assigned upgrade costs with interest. The SPP resubmitted a proposal on April 29, 2020 without this limited recovery, and with the alternative rate mechanism, and the FERC approved it on June 30, 2020, effective July 1, 2020. No party sought rehearing of the order, and it is now final. This order would only prospectively impact OG&E and its recovery of any future upgrade costs that it may incur as a project sponsor. All of the existing projects that are eligible to receive revenue credits under Attachment Z2, which includes the $13.0 million at issue in OG&E's appeal as discussed above, will continue to do so. APSC Proceedings Arkansas 2020 Formula Rate Plan Filing On October 1, 2020, OG&E filed its third evaluation report under its Formula Rate Plan, and on January 28, 2021, OG&E entered into a non-unanimous settlement agreement with the APSC General Staff and the Office of the Arkansas Attorney General. The only non-signatory to the settlement agreement has agreed not to oppose the settlement. The settlement agreement includes a revenue increase of $6.7 million, which is the maximum amount statutorily allowed in this filing. Additionally, the settling parties will not object to OG&E's request for a finding that the Arkansas Series II grid modernization projects included in this filing are prudent in cost. A final order is requested from the APSC in March 2021, and new rates will become effective April 1, 2021. Disconnection Procedures Related to COVID-19 On September 17, 2020, the APSC issued Order No. 9 inviting comments from all jurisdictional utilities and any other interested stakeholders on specific questions related to whether a moratorium on service terminations should be lifted and if so, how the resumption of disconnections should occur. The APSC also ordered utilities to submit a detailed "Transitional Plan" outlining how utilities propose to reinstate routine service disconnection activities and collection of past due amounts once the moratorium is lifted. OG&E submitted its proposed Transitional Plan on October 14, 2020. The APSC General Staff thereafter filed reports for utilities that set forth recommendations as to the form of notice that should occur prior to lifting the moratorium and resuming disconnections, as well as payment arrangements that should be made available to customers. On February 8, 2021, the APSC issued Order No. 15 announcing a target date of May 3, 2021 to lift the moratorium on disconnections and requiring certain conditions and requirements that utilities must meet before disconnections may resume. Such requirements include, among other things, immediate communication to customers, notice periods for disconnections and deferred payment arrangements. In the interim, the APSC is expected to continue to review all information relevant to a discontinuation of the moratorium and is expected to issue an order on March 26, 2021, either confirming the lifting of the moratorium on disconnections, or extending the moratorium. OCC Proceedings Oklahoma Retail Electric Supplier Certified Territory Act Causes Several rural electric cooperative electricity suppliers have filed complaints with the OCC alleging that OG&E has violated the Oklahoma Retail Electric Supplier Certified Territory Act. OG&E believes it is lawfully serving customers specifically exempted from this act and has presented evidence and testimony to the OCC supporting its position. There have been five complaint cases initiated at the OCC, and the OCC has issued decisions on each of them. The OCC ruled in favor of the electric cooperatives in three of those cases and ruled in favor of OG&E in two of those cases. All five of those cases have been appealed to the Oklahoma Supreme Court, where they have been made companion cases but will be individually briefed and have individual final decisions. If the Oklahoma Supreme Court ultimately were to find that some or all of the customers being served are not exempted from the Oklahoma Retail Electric Supplier Certified Territory Act, OG&E would have to evaluate the recoverability of some plant investments made to serve these customers. The total amount of OG&E's plant investments made to serve the customers in all five cases is approximately $28.0 million , of which $11.7 million applies to the three cases where the OCC ruled in favor of the electric cooperatives. In addition to the evaluation of the recoverability of the investments, OG&E may also be required to reimburse certified territory suppliers for an amount of lost revenue. The amount of such lost revenue would depend on how the OCC calculates the revenue requirement but could range from approximately $14.5 million to $21.7 million for all five cases, of which $1.4 million to $2.3 million would apply to the three cases where the OCC ruled in favor of the electric cooperatives. October 2020 Storm Examination In October 2020, a major ice storm moved through OG&E's service territory which caused significant damage to the system. On November 17, 2020, the Public Utility Division of the OCC initiated an examination and review of all distribution utilities and cooperatives affected by the storm into the mitigation efforts, restoration processes and proposed improvements for future related or similar events. Respondents are required to provide certain information related to the examination, and the OCC may request additional relief as the examination proceeds. No procedural schedule has been proposed currently; however, OG&E is responding to discovery requests. February 2021 Extreme Cold Weather Event In February 2021, OG&E's service territory experienced an unprecedented, prolonged, cold spell that resulted in record winter peak demand for electricity and extreme natural gas and purchased power prices. OG&E's natural gas costs for the month of February 2021 exceeded the total cost for all of 2020. Fuel and purchased power costs are recovered through OG&E's Oklahoma and Arkansas fuel adjustment clauses. Estimates of the total regulatory asset for fuel and purchased power costs that will be recorded are still under development but are expected to be in the range of $800.0 million to $1.0 billion. For approximately 58,000 guaranteed flat bill customers, representing approximately three percent of load, OG&E may be unable to seek recovery for the incremental fuel and purchased power costs that are included in customers' guaranteed flat bill agreements which would result in a loss to OG&E. Full impacts cannot be determined until all settlements and invoices are received for this period. While borrowing availability still exists within the Registrants' credit facilities, OGE Energy has secured a commitment for $1.0 billion in additional short-term financing to provide additional liquidity to help cover these increased fuel and purchased power costs. On February 24, 2021, OG&E submitted an application to the OCC outlining a two-step approach for regulatory treatment for the fuel and purchased power costs associated with the unprecedented weather event. The steps include: (i) an intra-year fuel clause increase to be effective April 1, 2021; and (ii) a request for regulatory asset treatment at OG&E's weighted average cost of capital for the remaining fuel and purchased power costs. OG&E anticipates making a similar filing with the APSC.

Schedule II

Schedule II	9 Months Ended
	Sep. 30, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	SCHEDULE II - Valuation and Qualifying Accounts Additions Description Balance at Beginning of Period Charged to Costs and Expenses Deductions (A) Balance at End of Period (In millions) Balance at December 31, 2018 Reserve for Uncollectible Accounts $ 1.5 $ 3.4 $ 3.2 $ 1.7 Balance at December 31, 2019 Reserve for Uncollectible Accounts $ 1.7 $ 2.2 $ 2.4 $ 1.5 Balance at December 31, 2020 Reserve for Uncollectible Accounts $ 1.5 $ 3.0 $ 1.9 $ 2.6

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation, Policy [Policy Text Block]	Organization OGE Energy is a holding company with investments in energy and energy services providers offering physical delivery and related services for both electricity and natural gas primarily in the south central U.S. OGE Energy conducts these activities through two business segments: (i) electric utility and (ii) natural gas midstream operations. The accounts of OGE Energy and its wholly-owned subsidiaries, including OG&E, are included in OGE Energy's consolidated financial statements. All intercompany transactions and balances are eliminated in such consolidation. OGE Energy generally uses the equity method of accounting for investments where its ownership interest is between 20 percent and 50 percent and it lacks the power to direct activities that most significantly impact economic performance. OG&E . OGE Energy's electric utility operations are conducted through OG&E, which generates, transmits, distributes and sells electric energy in Oklahoma and western Arkansas. OG&E's rates are subject to regulation by the OCC, the APSC and the FERC. OG&E was incorporated in 1902 under the laws of the Oklahoma Territory and is a wholly-owned subsidiary of OGE Energy. OG&E is the largest electric utility in Oklahoma, and its franchised service territory includes Fort Smith, Arkansas and the surrounding communities. OG&E sold its retail natural gas business in 1928 and is no longer engaged in the natural gas distribution business. Enable. OGE Energy's natural gas midstream operations segment represents OGE Energy's investment in Enable. The investment in Enable is held through wholly-owned subsidiaries and ultimately OGE Holdings. Enable is primarily engaged in the business of gathering, processing, transporting and storing natural gas. Enable's natural gas gathering and processing assets are strategically located in four states and serve natural gas production in the Anadarko, Arkoma and Ark-La-Tex Basins. Enable also owns crude oil gathering assets in the Anadarko and Williston Basins. Enable has intrastate natural gas transportation and storage assets that are located in Oklahoma as well as interstate assets that extend from western Oklahoma and the Texas Panhandle to Louisiana, from Louisiana to Illinois and from Louisiana to Alabama. Enable's general partner is equally controlled by OGE Energy and CenterPoint, who each have 50 percent management ownership. Based on the 50/50 management ownership, with neither company having control, OGE Energy accounts for its interest in Enable using the equity
Public Utilities, Policy [Policy Text Block]	Accounting Records The accounting records of OG&E are maintained in accordance with the Uniform System of Accounts prescribed by the FERC and adopted by the OCC and the APSC. Additionally, OG&E, as a regulated utility, is subject to accounting principles for certain types of rate-regulated activities, which provide that certain incurred costs that would otherwise be charged to expense can be deferred as regulatory assets, based on the expected recovery from customers in future rates. Likewise, certain actual or anticipated credits that would otherwise reduce expense can be deferred as regulatory liabilities, based on the expected flowback to customers in future rates. Management's expected recovery of deferred costs and flowback of deferred credits generally results from specific decisions by regulators granting such ratemaking treatment. OG&E records certain incurred costs and obligations as regulatory assets or liabilities if, based on regulatory orders or other available evidence, it is probable that the costs or obligations will be included in amounts allowable for recovery or refund in future rates.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents
Allowance for Uncollectible Accounts Receivable, Policy	Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is generally calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off and is adjusted for current conditions and supportable forecasts as necessary. To the extent the historical collection rates, when incorporating forecasted conditions, are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized, such as in response to COVID-19 impacts. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the balance sheets and is included in Other Operation and Maintenance Expense in the statements of income. The allowance for uncollectible accounts receivable was $2.6 million and $1.5 million at December 31, 2020 and 2019, respectively.
Inventory, Policy [Policy Text Block]	Fuel Inventories Fuel inventories for the generation of electricity consist of coal, natural gas and oil. OG&E uses the weighted-average cost method of accounting for inventory that is physically added to or withdrawn from storage or stockpiles. The amount of fuel inventory was $36.5 million and $46.3 million at December 31, 2020 and 2019, respectively.
Property, Plant and Equipment, Policy [Policy Text Block]	Property, Plant and Equipment
Depreciation and Amortization, Policy [Policy Text Block]	Depreciation and Amortization The provision for depreciation, which was 2.6 percent and 2.7 percent of the average depreciable utility plant for 2020 and 2019, respectively, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2021, the provision for depreciation is projected to be 2.6 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2020, 99.0 percent will be amortized over 10.4 years with the remaining 1.0 percent of the intangible plant balance at December 31, 2020 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life, and $3.3 million for certain transmission substation facilities in OG&E's service territory, which is being amortized over a 37 to 59 year period.
Equity Method Investments [Policy Text Block]	Investment in Unconsolidated Affiliates OGE Energy's investment in Enable is considered to be a variable interest entity because the owners of the equity at risk in this entity have disproportionate voting rights in relation to their obligations to absorb the entity's expected losses or to receive its expected residual returns. However, OGE Energy is not considered the primary beneficiary of Enable since it does not have the power to direct the activities of Enable that are considered most significant to the economic performance of Enable; therefore, OGE Energy accounts for its investment in Enable using the equity method of accounting. Under the equity method, the investment will be adjusted each period for contributions made, distributions received and OGE Energy's share of the investee's comprehensive income as adjusted for basis differences. OGE Energy's maximum exposure to loss related to Enable is limited to its equity investment in Enable at December 31, 2020 as presented in Note 14. OGE Energy evaluates its equity method investments for impairment when events or changes in circumstances indicate there is a loss in value of the investment that is other than a temporary decline. When indicators exist, the fair value is estimated and compared to the investment carrying value, and if any impairment is judgmentally determined to be other than temporary, the carrying value of the investment is written down to fair value. OGE Energy determined, effective March 31, 2020, that an other than temporary decline in the value of OGE Energy's investment in Enable had occurred. Further information detailing the results of OGE Energy's impairment analysis and fair value measurement can be found in Notes 5 and 7, respectively. OGE Energy considers distributions received from Enable which do not exceed cumulative equity in earnings subsequent to the date of investment to be a return on investment and are classified as operating activities in the statements of cash flows. OGE Energy considers distributions received from Enable in excess of cumulative equity in earnings subsequent to the date of investment to be a return of investment and are classified as investing activities in the statements of cash flows.
Asset Retirement Obligation [Policy Text Block]	Asset Retirement ObligationsOG&E has asset retirement obligations primarily associated with the removal of company-owned wind turbines on leased land, as well as the removal of asbestos from certain power generating stations. OG&E has recorded asset retirement obligations that are being accreted over their respective lives ranging from five to 68 years. Asset retirement obligations are included in Other Deferred Credits in the Registrants' balance sheets.
Allowance for Funds Used During Construction, Policy [Policy Text Block]	Allowance for Funds Used During Construction
Collection of Sales Tax, Policy [Policy Text Block]	Collection of Sales Tax
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition General OG&E recognizes revenue from electric sales when power is delivered to customers. The performance obligation to deliver electricity is generally created and satisfied simultaneously, and the provisions of the regulatory-approved tariff determine the charges OG&E may bill the customer, payment due date and other pertinent rights and obligations of both parties. OG&E measures its customers' metered usage and sends bills to its customers throughout each month. As a result, there is a significant amount of customers' electricity consumption that has not been billed at the end of each month. OG&E accrues an estimate of the revenues for electric sales delivered since the latest billings. Unbilled revenue is presented in Accrued Unbilled Revenues in the balance sheets and in Revenues from Contracts with Customers in the statements of income based on estimates of usage and prices during the period. The estimates that management uses in this calculation could vary from the actual amounts to be paid by customers. Integrated Market and Transmission OG&E currently owns and operates transmission and generation facilities as part of a vertically integrated utility. OG&E is a member of the SPP regional transmission organization and has transferred operational authority, but not ownership, of OG&E's transmission facilities to the SPP. The SPP has implemented FERC-approved regional day-ahead and real-time markets for energy and operating services, as well as associated transmission congestion rights. Collectively, the three markets operate together under the global name, SPP Integrated Marketplace. OG&E represents owned and contracted generation assets and customer load in the SPP Integrated Marketplace for the sole benefit of its customers. OG&E has not participated in the SPP Integrated Marketplace for any speculative trading activities. OG&E records the SPP Integrated Marketplace transactions as sales or purchases per FERC Order 668, which requires that purchases and sales be recorded on a net basis for each settlement period of the SPP Integrated Marketplace. Purchases and sales are based on the fixed transaction price determined by the market at the time of the purchase or sale and the MWh quantity purchased or sold. These results are reported as Revenues from Contracts with Customers or Cost of Sales in the statements of income. OG&E revenues, expenses, assets and liabilities may be adversely affected by changes in the organization, operating and regulation by the FERC or the SPP. OG&E's transmission revenues are generated by the use of OG&E's transmission network by the SPP, which operates the network, on behalf of other transmission owners. OG&E recognizes revenue on the sale of transmission service to its customers over time as the service is provided in the amount OG&E has a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by OG&E's FERC-approved formula transmission rates along with other SPP-specific charges and the megawatt quantity reserved. Other Revenues Other Revenues in the statements of income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either
Fuel Adjustment Clauses, Policy [Policy Text Block]	Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC.
Lessee, Leases	LeasesThe Registrants evaluate all contracts under ASC 842 to determine if the contract is or contains a lease and to determine classification as an operating or finance lease. If a lease is identified, the Registrants recognize a right-of-use asset and a lease liability in their balance sheets. The Registrants recognize and measure a lease liability when they conclude the contract contains an identified asset that the Registrants control through having the right to obtain substantially all of the economic benefits and the right to direct the use of the identified asset. The liability is equal to the present value of lease payments, and the asset is based on the liability, subject to adjustment, such as for initial direct costs. Further, the Registrants utilize an incremental borrowing rate for purposes of measuring lease liabilities, if the discount rate is not implicit in the lease. To calculate the incremental borrowing rate, the Registrants start with a current pricing report for their senior unsecured notes, which indicates rates for periods reflective of the lease term, and adjust for the effects of collateral to arrive at the secured incremental borrowing rate. As permitted by ASC 842, the Registrants made an accounting policy election to not apply the balance sheet recognition requirements to short-term leases and to not separate lease components from non-lease components when recognizing and measuring lease liabilities. For income statement purposes, the Registrants record operating lease expense on a straight-line basis.
Income Taxes, Policy [Policy Text Block]	Income Taxes OGE Energy files consolidated income tax returns in the U.S. federal jurisdiction and various state jurisdictions. OG&E is a part of the consolidated tax return of OGE Energy. Income taxes are generally allocated to each company in the affiliated group, including OG&E, based on its stand-alone taxable income or loss. Federal investment tax credits previously claimed on electric utility property have been deferred and will be amortized to income over the life of the related property. The Registrants use the asset and liability method of accounting for income taxes. Under this method, a deferred tax asset or liability is recognized for the estimated future tax effects attributable to temporary differences between the financial statement basis and the tax basis of assets and liabilities as well as tax credit carry forwards and net operating loss carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period of the change. The Registrants recognize interest related to unrecognized tax benefits in Interest Expense and recognize penalties in Other Expense in the statements of income.
Accrued Vacation, Policy [Policy Text Block]	Accrued Vacation The Registrants accrue vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.
Environmental Costs, Policy [Policy Text Block]	Accruals for environmental costs are recognized when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. Costs are charged to expense or deferred as a regulatory asset based on expected recovery from customers in future rates, if they relate to the remediation of conditions caused by past operations or if they are not expected to mitigate or prevent contamination from future operations. Where environmental expenditures relate to facilities currently in use, such as pollution control equipment, the costs may be capitalized and depreciated over the future service periods. Estimated remediation costs are recorded at undiscounted amounts, independent of any insurance or rate recovery, based on prior experience, assessments and current technology. Accrued obligations are regularly adjusted as environmental assessments and estimates are revised and remediation efforts proceed. For sites where OG&E has been designated as one of several potentially responsible parties, the amount accrued represents OG&E's estimated share of the cost. OG&E had $25.0 million and $18.7 million in accrued environmental liabilities at December 31, 2020 and 2019, respectively, which are included in OG&E's asset retirement obligations.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Fair Value Measurements The classification of the Registrants' fair value measurements requires judgment regarding the degree to which market data is observable or corroborated by observable market data. GAAP establishes a fair value hierarchy that prioritizes the inputs used to measure fair value based on observable and unobservable data. The hierarchy categorizes the inputs into three levels, with the highest priority given to quoted prices in active markets for identical unrestricted assets or liabilities (Level 1) and the lowest priority given to unobservable inputs (Level 3). Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels defined in the fair value hierarchy are as follows: Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the reporting entity's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).
Share-based Compensation, Option and Incentive Plans, Policy [Policy Text Block]	Performance Units Under the Stock Incentive Plan, OGE Energy has issued performance units which represent the value of one share of OGE Energy's common stock. The performance units provide for accelerated vesting if there is a change in control (as defined in the Stock Incentive Plan). Each performance unit is subject to forfeiture if the recipient terminates employment with OGE Energy or a subsidiary prior to the end of the primarily three-year award cycle for any reason other than death, disability or retirement. In the event of death, disability or retirement, a participant will receive a prorated payment based on such participant's number of full months of service during the award cycle, further adjusted based on the achievement of the performance goals during the award cycle. The Registrants estimate expected forfeitures in accounting for performance unit compensation expense. The performance units granted based on total shareholder return are contingently awarded and will be payable in shares of OGE Energy's common stock subject to the condition that the number of performance units, if any, earned by the employees upon the expiration of a primarily three-year award cycle (i.e., three-year cliff vesting period) is dependent on OGE Energy's total shareholder return ranking relative to a peer group of companies. The performance units granted based on earnings per share are contingently awarded and will be payable in shares of OGE Energy's common stock based on OGE Energy's earnings per share growth over a primarily three-year award cycle (i.e., three-year cliff vesting period) compared to a target set at the time of the grant by the Compensation Committee of OGE Energy's Board of Directors. All of these performance units are classified as equity in the balance sheets. If there is no or only a partial payout for the performance units at the end of the award cycle, the unearned performance units are cancelled. Payout requires approval of the Compensation Committee of OGE Energy's Board of Directors. Payouts, if any, are all made in common stock and are considered made when the payout is approved by the Compensation Committee. Performance Units – Total Shareholder Return Restricted Stock Units Under the Stock Incentive Plan, OGE Energy has issued restricted stock units to certain existing non-officer employees as well as other executives upon hire to attract and retain individuals to be competitive in the marketplace, and as of the 2019 grant cycle, restricted stock units are granted in lieu of performance units based on earnings per share. The restricted stock units vest primarily in a three-year award cycle (i.e., three-year cliff vesting period). Prior to vesting, each restricted stock unit is subject to forfeiture if the recipient ceases to render substantial services to OGE Energy or a subsidiary. These restricted stock units may not be sold, assigned, transferred or pledged and are subject to a risk of forfeiture. The fair value of the restricted stock units was based on the closing market price of OGE Energy's common stock on the grant date. Compensation expense for the restricted stock units is a fixed amount determined at the grant date fair value and is recognized as services are rendered by employees over a primarily three-year vesting period. Also, for those restricted stock units that vest in one-third annual increments over a three-year cycle, OGE Energy treats its restricted stock units as multiple separate awards by recording compensation expense separately for each tranche whereby a substantial portion of the expense is recognized in the earlier years in the requisite service period.
Earnings Per Share, Policy [Policy Text Block]	Earnings (Loss) Per Share
Pension and Other Postretirement Plans, Policy [Policy Text Block]	Pension Plan and Restoration of Retirement Income Plan It is OGE Energy's policy to fund the Pension Plan on a current basis based on the net periodic pension expense as determined by OGE Energy's actuarial consultants. Such contributions are intended to provide not only for benefits attributed to service to date but also for those expected to be earned in the future. OGE Energy made a $20.0 million contribution to its Pension Plan in both 2020 and 2019, of which $10.0 million and $5.0 million was attributed to OG&E in 2020 and 2019, respectively. In January 2021, OGE Energy made a $40.0 million contribution to its Pension Plan and has not determined whether it will need to make any additional contributions to the Pension Plan in 2021. Any contribution to the Pension Plan during 2021 would be a discretionary contribution, anticipated to be in the form of cash, and is not required to satisfy the minimum regulatory funding requirement specified by the Employee Retirement Income Security Act of 1974, as amended. OGE Energy could be required to make additional contributions if the value of its pension trust and postretirement benefit plan trust assets are adversely impacted by a major market disruption in the future. OGE Energy provides a Restoration of Retirement Income Plan to those participants in OGE Energy's Pension Plan whose benefits are subject to certain limitations of the Code. Participants in the Restoration of Retirement Income Plan receive the same benefits that they would have received under OGE Energy's Pension Plan in the absence of limitations imposed by the federal tax laws. The Restoration of Retirement Income Plan is intended to be an unfunded plan. OG&E's employees participate in OGE Energy's Pension Plan and Restoration of Retirement Income Plan. Postretirement Benefit Plans In addition to providing pension benefits, OGE Energy provides certain medical and life insurance benefits for eligible retired members. Regular, full-time, active employees hired prior to February 1, 2000 whose age and years of credited service total or exceed 80 or have attained at least age 55 with 10 or more years of service at the time of retirement are entitled to postretirement medical benefits, while employees hired on or after February 1, 2000 are not entitled to postretirement medical benefits. Eligible retirees must contribute such amount as OGE Energy specifies from time to time toward the cost of coverage for postretirement benefits. The benefits are subject to deductibles, co-payment provisions and other limitations. OG&E charges postretirement benefit costs to expense and includes an annual amount as a component of the cost-of-service in future ratemaking proceedings.
Postemployment Benefit Plans, Policy [Policy Text Block]	Post-Employment Benefit Plan Disabled employees receiving benefits from OGE Energy's Group Long-Term Disability Plan are entitled to continue participating in OGE Energy's Medical Plan along with their dependents. The post-employment benefit obligation represents the actuarial present value of estimated future medical benefits that are attributed to employee service rendered prior to the date as of which such information is presented. The obligation also includes future medical benefits expected to be paid to current employees participating in the Group Long-Term Disability Plan and their dependents, as defined in OGE Energy's Medical Plan.
Plan Investments, Policies and Strategies, Policy [Policy Text Block]	Pension Plan Investments, Policies and Strategies The Pension Plan assets are held in a trust which follows an investment policy and strategy designed to reduce the funded status volatility of the Plan by utilizing liability driven investing. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The investment policy follows a glide path approach that shifts a higher portfolio weighting to fixed income as the Plan's funded status increases. The following table presents the targeted fixed income and equity allocations at different funded status levels. Projected Benefit Obligation Funded Status Thresholds <90% 95% 100% 105% 110% 115% 120% Fixed income 50% 58% 65% 73% 80% 85% 90% Equity 50% 42% 35% 27% 20% 15% 10% Total 100% 100% 100% 100% 100% 100% 100% Within the portfolio's overall allocation to equities, the funds are allocated according to the guidelines in the following table. Asset Class Target Allocation Minimum Maximum Domestic Large Cap Equity 40% 35% 60% Domestic Mid-Cap Equity 15% 5% 25% Domestic Small-Cap Equity 25% 5% 30% International Equity 20% 10% 30% OGE Energy has retained an investment consultant responsible for the general investment oversight, analysis, monitoring investment guideline compliance and providing quarterly reports to certain of the Registrants' members and OGE Energy's Investment Committee. The various investment managers used by the trust operate within the general operating objectives as established in the investment policy and within the specific guidelines established for each investment manager's respective portfolio. The portfolio is rebalanced at least on an annual basis to bring the asset allocations of various managers in line with the target asset allocation listed above. More frequent rebalancing may occur if there are dramatic price movements in the financial markets which may cause the trust's exposure to any asset class to exceed or fall below the established allowable guidelines. To evaluate the progress of the portfolio, investment performance is reviewed quarterly. It is, however, expected that performance goals will be met over a full market cycle, normally defined as a three- to five-year period. Analysis of performance is within the context of the prevailing investment environment and the advisors' investment style. The goal of the trust is to provide a rate of return consistently from three percent to five percent over the rate of inflation (as measured by the national Consumer Price Index) on a fee adjusted basis over a typical market cycle of no less than three years and no more than five years. Each investment manager is expected to outperform its respective benchmark. The following table presents a list of each asset class utilized with appropriate comparative benchmark(s) each manager is evaluated against and the focus of the asset class. Asset Class Comparative Benchmark(s) Focus of Asset Class Active Duration Fixed Income (A)(B) Bloomberg Barclays Aggregate l Maximize risk-adjusted performance while providing long bond exposure managed according to the manager's forecast on interest rates. l All invested assets must reach at or above Baa3 or BBB- investment grade. l Limited five percent exposure to any single issuer, except the U.S. Government or affiliates. Long Duration Fixed Income (A)(B) Duration blended Barclays Long Government/Credit & Barclays Universal l Maximize risk-adjusted performance. l At least 75 percent of invested assets much reach at or above Baaa3 or BBB- investment grade. l Limited five percent exposure to any single issuer, except the U.S. Government or affiliates. l May invest up to 10 percent of the market value in convertible bonds as long as quality guidelines are met. l May invest up to 15 percent of the market value in private placement, including 144A securities with or without registration rights and allow for futures to be traded in the portfolio. Equity Index (B)(C) Standard & Poor's 500 Index l Focus on replicating the performance of the S&P 500 Index. Mid-Cap Equity (B)(C) Russell Midcap Index l Focus on undervalued stocks expected to earn average return and pay out higher than average dividends. l Invest in companies with market capitalizations lower than average company on public exchanges: l Price/earnings ratio at or near referenced index; l Small dividend yield and return on equity at or near referenced index; and l Earnings per share growth rate at or near referenced index. Small-Cap Equity (B)(C) Russell 2000 Index International Equity (D) Morgan Stanley Capital International ACWI ex-U.S. l Invest in non-dollar denominated equity securities. l Diversify the overall trust investments. (A) Investment grades are by Moody's Investors Service, S&P Global Ratings or Fitch Ratings. (B) The purchase of any of OGE Energy's equity, debt or other securities is prohibited. (C) No more than five percent can be invested in any one stock at the time of purchase and no more than 10 percent after accounting for price appreciation. Options or financial futures may not be purchased unless prior approval from OGE Energy's Investment Committee is received. The purchase of securities on margin, securities lending, private placement purchases and venture capital purchases are prohibited. The aggregate positions in any company may not exceed one percent of the fair market value of its outstanding stock. (D) The manager of this asset class is required to operate under certain restrictions including regional constraints, diversification requirements and percentage of U.S. securities. All securities are freely traded on a recognized stock exchange, and there are no over-the-counter derivatives. The following investment categories are excluded: options (other than traded currency options), commodities, futures (other than currency futures or currency hedging), short sales/margin purchases, private placements, unlisted securities and real estate (but not real estate shares).
Pension and Other Postretirement Plans, Nonpension Benefits, Policy [Policy Text Block]	401(k) Plan OGE Energy provides a 401(k) Plan, and each regular full-time employee of OGE Energy or a participating affiliate is eligible to participate in the 401(k) Plan immediately upon hire. All other employees of OGE Energy or a participating affiliate are eligible to become participants in the 401(k) Plan after completing one year of service as defined in the 401(k) Plan. Participants may contribute each pay period any whole percentage between two percent and 19 percent of their compensation, as defined in the 401(k) Plan, for that pay period. Participants who have reached age 50 before the close of a year are allowed to make additional contributions referred to as "Catch-Up Contributions," subject to certain limitations of the Code. Participants may designate, at their discretion, all or any portion of their contributions as: (i) a before-tax contribution under Section 401(k) of the Code subject to the limitations thereof, (ii) a contribution made on a non-Roth after-tax basis or (iii) a Roth contribution. The 401(k) Plan also includes an eligible automatic contribution arrangement and provides for a qualified default investment alternative consistent with the U.S. Department of Labor regulations. Participants may elect, in accordance with the 401(k) Plan procedures, to have their future salary deferral rate to be automatically increased annually on a date and in an amount as specified by the participant in such election. For employees hired or rehired on or after December 1, 2009, OGE Energy contributes to the 401(k) Plan, on behalf of each participant, 200 percent of the participant's contributions up to five percent of compensation. No OGE Energy contributions are made with respect to a participant's Catch-Up Contributions, rollover contributions or with respect to a participant's contributions based on overtime payments, pay-in-lieu of overtime for exempt personnel, special lump-sum recognition awards and lump-sum merit awards included in compensation for determining the amount of participant contributions. Once made, OGE Energy's contribution may be directed to any available investment option in the 401(k) Plan. OGE Energy match contributions vest over a three-year period. After two years of service, participants become 20 percent vested in their OGE Energy contribution account and become fully vested on completing three years of service. In addition, participants fully vest when they are eligible for normal or early retirement under the Pension Plan requirements, in the event of their termination due to death or permanent disability or upon attainment of age 65 while employed by OGE Energy or its affiliates. OGE Energy contributed $18.2 million, $14.4 million and $13.2 million in 2020, 2019 and 2018, respectively, to the 401(k) Plan, of which $14.3 million, $11.0 million and $9.8 million, respectively, related to OG&E. Deferred Compensation Plan OGE Energy provides a nonqualified deferred compensation plan which is intended to be an unfunded plan. The plan's primary purpose is to provide a tax-deferred capital accumulation vehicle for a select group of management, highly compensated employees and non-employee members of OGE Energy's Board of Directors and to supplement such employees' 401(k) Plan contributions as well as offering this plan to be competitive in the marketplace. Eligible employees who enroll in the plan have the following deferral options: (i) eligible employees may elect to defer up to a maximum of 70 percent of base salary and 100 percent of annual bonus awards or (ii) eligible employees may elect a deferral percentage of base salary and bonus awards based on the deferral percentage elected for a year under the 401(k) Plan with such deferrals to start when maximum deferrals to the qualified 401(k) Plan have been made because of limitations in that plan. Eligible directors who enroll in the plan may elect to defer up to a maximum of 100 percent of directors' meeting fees and annual retainers. OGE Energy matches employee (but not non-employee director) deferrals to make up for any match lost in the 401(k) Plan because of deferrals to the deferred compensation plan and to allow for a match that would have been made under the 401(k) Plan on that portion of either the first six percent of total compensation or the first five percent of total compensation, depending on prior participant elections, deferred that exceeds the limits allowed in the 401(k) Plan. Matching credits vest based on years of service, with full vesting after three years or, if earlier, on retirement, disability, death, a change in control of OGE Energy or termination of the plan. Deferrals, plus any OGE Energy match, are credited to a recordkeeping account in the participant's name. Earnings on the deferrals are indexed to the assumed investment funds selected by the participant. In 2020, those investment options included an OGE Energy Common Stock fund, whose value was determined based on the stock price of OGE Energy's Common Stock. OGE Energy accounts for the contributions related to its executive officers in this plan as Accrued Benefit Obligations and accounts for the contributions related to OGE Energy's directors in this plan as Other Deferred Credits and Other Liabilities in the balance sheets. The investment associated with these contributions is accounted for as Other Property and Investments in the balance sheets. The appreciation of these investments is accounted for as Other Income, and the increase in the liability under the plan is accounted for as Other Expense in the statements of income.

Fair Value Measures and Disclos

Fair Value Measures and Disclosures (Policies)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurement, Policy	Nonrecurring Fair Value Measurements As further discussed in Note 5, OGE Energy recorded an impairment on its investment in Enable in March 2020. The nonrecurring fair value measurement consisted of calculating a 20-trading day volume weighted average price for Enable's common units through March 31, 2020. This method of valuation was determined to be representative of the fair value of Enable's common units as it incorporated market prices during the period and reduced the impact of volatility that a single day could represent. OGE Energy concluded that this valuation method resulted in a Level 3 nonrecurring fair value measurement.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Regulatory Assets and Liabilities [Table Text Block]	The following table presents a summary of OG&E's regulatory assets and liabilities. December 31 (In millions) 2020 2019 REGULATORY ASSETS Current: SPP cost tracker under recovery (A) $ 7.0 $ — Generation Capacity Replacement rider under recovery (A) 4.4 3.7 Fuel clause under recoveries — 39.5 Other (A) 8.4 5.5 Total current regulatory assets $ 19.8 $ 48.7 Non-current: Benefit obligations regulatory asset $ 164.9 $ 167.2 Deferred storm expenses 158.8 65.5 Sooner Dry Scrubbers 19.7 20.6 Pension tracker 18.1 2.3 Smart Grid 11.2 18.4 Unamortized loss on reacquired debt 9.7 10.6 Arkansas deferred pension expenses 9.3 8.0 Frontier Plant deferred expenses 6.4 — COVID-19 impacts 6.4 — Other 11.1 13.4 Total non-current regulatory assets $ 415.6 $ 306.0 REGULATORY LIABILITIES Current: Fuel clause over recoveries $ 28.6 $ 4.8 Oklahoma demand program rider over recovery (B) 1.5 2.0 Reserve for tax refund and interim surcharge (B) 0.8 12.7 SPP cost tracker over recovery (B) — 2.6 Other (B) 4.2 6.9 Total current regulatory liabilities $ 35.1 $ 29.0 Non-current: Income taxes refundable to customers, net $ 867.4 $ 899.2 Accrued removal obligations, net 316.8 318.5 Other 4.7 5.8 Total non-current regulatory liabilities $ 1,188.9 $ 1,223.5 (A) Included in Other Current Assets in the balance sheets.
Components of Benefit Obligation Regulatory Asset [Table Text Block]	The following table presents a summary of the components of the benefit obligations regulatory asset. December 31 (In millions) 2020 2019 Pension Plan and Restoration of Retirement Income Plan: Net loss $ 147.3 $ 160.5 Postretirement Benefit Plans: Net loss 26.2 23.3 Prior service cost (8.6) (16.6) Total $ 164.9 $ 167.2
Schedule of Jointly Owned Utility Plants [Table Text Block]	The following tables present OG&E's ownership interest in the jointly-owned McClain Plant and the jointly-owned Redbud Plant, and, as disclosed below, only OG&E's ownership interest is reflected in the property, plant and equipment and accumulated depreciation balances in these tables. The owners of the remaining interests in the McClain Plant and the Redbud Plant are responsible for providing their own financing of capital expenditures. Also, only OG&E's proportionate interests of any direct expenses of the McClain Plant and the Redbud Plant, such as fuel, maintenance expense and other operating expenses, are included in the applicable financial statement captions in the statements of income. December 31, 2020 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 257.1 $ 96.0 $ 161.1 Redbud Plant (A)(B) 51 % $ 531.8 $ 181.9 $ 349.9 (A) Construction work in progress was $0.1 million and $1.8 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $67.3 million. December 31, 2019 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 254.4 $ 83.5 $ 170.9 Redbud Plant (A)(B) 51 % $ 529.9 $ 159.0 $ 370.9 (A) Construction work in progress was $0.2 million and $1.4 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million.
Property, Plant and Equipment [Table Text Block]	The following tables present the Registrants' major classes of property, plant and equipment and related accumulated depreciation. December 31, 2020 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment OG&E: Distribution assets $ 4,809.9 $ 1,422.1 $ 3,387.8 Electric generation assets (A) 4,932.2 1,713.6 3,218.6 Transmission assets (B) 2,944.6 591.7 2,352.9 Intangible plant 254.1 153.9 100.2 Other property and equipment 495.3 186.3 309.0 OG&E property, plant and equipment 13,436.1 4,067.6 9,368.5 Non-OG&E property, plant and equipment 6.1 — 6.1 Total OGE Energy property, plant and equipment $ 13,442.2 $ 4,067.6 $ 9,374.6 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $67.3 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.9 million. December 31, 2019 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment OG&E: Distribution assets $ 4,468.6 $ 1,381.1 $ 3,087.5 Electric generation assets (A) 4,838.6 1,601.0 3,237.6 Transmission assets (B) 2,901.1 565.5 2,335.6 Intangible plant 225.2 145.4 79.8 Other property and equipment 473.1 175.1 298.0 OG&E property, plant and equipment 12,906.6 3,868.1 9,038.5 Non-OG&E property, plant and equipment 6.1 — 6.1 Total OGE Energy property, plant and equipment $ 12,912.7 $ 3,868.1 $ 9,044.6 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.8 million.
Schedule of Change in Asset Retirement Obligation [Table Text Block]	The following table presents changes to OG&E's asset retirement obligations during the years ended December 31, 2020 and 2019. (In millions) 2020 2019 Balance at January 1 $ 73.5 $ 83.9 Accretion expense 0.5 1.0 Revisions in estimated cash flows (A) 5.8 (2.4) Liabilities settled (B) (0.2) (9.0) Balance at December 31 $ 79.6 $ 73.5 (A) Assumptions changed related to the estimated timing and estimated cost of the removal of asbestos at OG&E's generating facilities.
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table presents changes in the components of accumulated other comprehensive income (loss) attributable to OGE Energy during 2019 and 2020. All amounts below are presented net of tax. Pension Plan and Restoration of Retirement Income Plan Postretirement Benefit Plans (In millions) Net Gain Net Gain (Loss) Prior Service Cost (Credit) Other Comprehensive Loss from Unconsolidated Affiliates Total Balance at December 31, 2018 $ (38.8) $ 4.6 $ 5.3 $ — $ (28.9) Other comprehensive loss before reclassifications (8.3) (0.2) — (0.6) (9.1) Amounts reclassified from accumulated other comprehensive income (loss) 3.4 (0.2) (1.7) — 1.5 Settlement cost 8.6 — — — 8.6 Net current period other comprehensive income (loss) 3.7 (0.4) (1.7) (0.6) 1.0 Balance at December 31, 2019 (35.1) 4.2 3.6 (0.6) (27.9) Other comprehensive income (loss) before reclassifications (5.1) (2.4) — (0.7) (8.2) Amounts reclassified from accumulated other comprehensive income (loss) 3.9 (0.1) (1.7) — 2.1 Curtailment cost — (0.3) — — (0.3) Settlement cost 2.2 — — — 2.2 Net current period other comprehensive income (loss) 1.0 (2.8) (1.7) (0.7) (4.2) Balance at December 31, 2020 $ (34.1) $ 1.4 $ 1.9 $ (1.3) $ (32.1)
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following table presents significant amounts reclassified out of accumulated other comprehensive income (loss) by the respective line items in net income (loss) during the years ended December 31, 2020 and 2019. Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in Year Ended December 31, (In millions) 2020 2019 Amortization of Pension Plan and Restoration of Retirement Income Plan items: Actuarial losses $ (5.1) $ (4.5) (A) Settlement cost (2.9) (11.3) (A) (8.0) (15.8) Income (Loss) Before Taxes (1.9) (3.8) Income Tax Expense (Benefit) $ (6.1) $ (12.0) Net Income (Loss) Amortization of postretirement benefit plans items: Prior service credit $ 2.3 $ 2.3 (A) Curtailment cost 0.4 — (A) Actuarial gains 0.1 0.2 (A) 2.8 2.5 Income (Loss) Before Taxes 0.7 0.6 Income Tax Expense (Benefit) $ 2.1 $ 1.9 Net Income (Loss) Total reclassifications for the period, net of tax $ (4.0) $ (10.1) Net Income (Loss) (A) These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost (see Note 13 for additional information).

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	The following table presents OG&E's revenues from contracts with customers disaggregated by customer classification. OG&E's operating revenues disaggregated by customer classification can be found in "OG&E (Electric Utility) Results of Operations" within "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations." Year Ended December 31, (In millions) 2020 2019 2018 Residential $ 842.7 $ 865.8 $ 877.8 Commercial 465.6 486.6 500.0 Industrial 192.6 217.8 228.9 Oilfield 169.2 200.4 190.4 Public authorities and street light 172.3 190.3 197.4 System sales revenues 1,842.4 1,960.9 1,994.5 Provision for rate refund 3.8 (0.9) (6.0) Integrated market 49.6 38.4 48.7 Transmission 143.3 148.0 147.4 Other 30.7 29.1 27.1 Revenues from contracts with customers $ 2,069.8 $ 2,175.5 $ 2,211.7

Leases, Codification Topic 842

Leases, Codification Topic 842 (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lease, Cost	The following table presents amounts recognized for operating leases in the Registrants' cash flow statements and balance sheets and supplemental information related to those amounts recognized. OGE Energy OG&E Year Ended December 31, Year Ended December 31, (In millions) 2020 2019 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 6.4 $ 5.6 $ 5.5 $ 4.8 Right-of-use assets obtained in exchange for new operating lease liabilities $ 1.4 $ 10.7 $ 1.4 $ 10.7 (Dollars in millions) December 31, 2020 December 31, 2019 December 31, 2020 December 31, 2019 Right-of-use assets at period end (A) $ 37.6 $ 40.9 $ 37.0 $ 39.6 Operating lease liabilities at period end (B) $ 42.3 $ 45.8 $ 41.7 $ 44.3 Operating lease weighted-average remaining lease term (in years) 12.5 13.1 12.7 13.5 Operating lease weighted-average discount rate 3.9 % 3.9 % 3.9 % 3.9 % (A) Included in Property, Plant and Equipment in the Registrants' balance sheets. (B) Included in Other Deferred Credits and Other Liabilities in the Registrants' balance sheets. The following table presents a maturity analysis of the Registrants' operating lease liabilities. Future minimum operating lease payments as of December 31: OGE Energy OG&E (In millions) 2021 $ 6.3 $ 5.7 2022 5.7 5.7 2023 5.1 5.1 2024 3.2 3.2 2025 3.0 3.0 Thereafter 31.7 31.7 Total future minimum lease payments 55.0 54.4 Less: Imputed interest 12.7 12.7 Present value of net minimum lease payments $ 42.3 $ 41.7

Investment in Unconsolidated _2

Investment in Unconsolidated Affiliate (Tables)	12 Months Ended
	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Summarized Balance Sheet Financial Information, Equity Method Investment [Table Text Block]	The following tables present summarized unaudited financial information for 100 percent of Enable as of December 31, 2020 and 2019 and for the years ended December 31, 2020, 2019 and 2018. December 31, Balance Sheet 2020 2019 (In millions) Current assets $ 381 $ 389 Non-current assets $ 11,348 $ 11,877 Current liabilities $ 582 $ 780 Non-current liabilities $ 4,052 $ 4,077
Summarized Income Statement Financial Information, Equity Method Investment [Table Text Block]	Year Ended December 31, Income Statement 2020 2019 2018 (In millions) Total revenues $ 2,463 $ 2,960 $ 3,431 Cost of natural gas and NGLs $ 965 $ 1,279 $ 1,819 Operating income $ 465 $ 569 $ 648 Net income $ 52 $ 360 $ 485
Reconciliation of Equity in Earnings of Unconsolidated Affiliates [Table Text Block]	The following table presents a reconciliation of OGE Energy's equity in earnings (losses) of unconsolidated affiliates for the years ended December 31, 2020, 2019 and 2018. For further discussion of Enable's net income, see "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations - Results of Operations - OGE Holdings (Natural Gas Midstream Operations)." Year Ended December 31, (In millions) 2020 2019 2018 Enable net income $ 52.0 $ 360.0 $ 485.3 OGE Energy's percent ownership at period end 25.5 % 25.5 % 25.6 % OGE Energy's portion of Enable net income $ 13.2 $ 91.8 $ 124.4 Amortization of basis difference and dilution recognition (A) 98.8 22.1 28.4 Impairment of OGE Energy's equity method investment in Enable (780.0) — — Equity in earnings (losses) of unconsolidated affiliates (B) $ (668.0) $ 113.9 $ 152.8 (A) Includes loss on dilution, net of proportional basis difference recognition. (B) 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.
Reconciliation of Basis Difference [Table Text Block]	The following table presents a reconciliation of the difference between OGE Energy's investment in Enable and its underlying equity in the net assets of Enable (basis difference) from December 31, 2019 to December 31, 2020. The basis difference is being amortized over approximately 30 years. (In millions) Basis difference at December 31, 2019 $ 652.5 Amortization of basis difference (A) (100.2) Impairment of OGE Energy's equity method investment in Enable 780.0 Basis difference at December 31, 2020 $ 1,332.3 (A) Includes proportional basis difference recognition due to dilution.
Schedule of Related Party Transactions [Table Text Block]	The following table presents summarized related party transactions between OG&E and Enable during the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, (In millions) 2020 2019 2018 Operating revenues: Electricity to power electric compression assets $ 15.1 $ 15.9 $ 16.3 Cost of sales: Natural gas transportation services $ 32.8 $ 41.2 $ 37.9 Natural gas purchases (sales) $ 2.7 $ (6.0) $ (3.2)

Related Party Disclosures (Tabl

Related Party Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	The following table presents summarized related party transactions between OG&E and Enable during the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, (In millions) 2020 2019 2018 Operating revenues: Electricity to power electric compression assets $ 15.1 $ 15.9 $ 16.3 Cost of sales: Natural gas transportation services $ 32.8 $ 41.2 $ 37.9 Natural gas purchases (sales) $ 2.7 $ (6.0) $ (3.2)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping [Table Text Block]	The following table presents the carrying amount and fair value of the Registrants' financial instruments at December 31, 2020 and 2019, as well as the classification level within the fair value hierarchy. 2020 2019 December 31 (In millions) Carrying Amount Fair Carrying Amount Fair Classification Long-term Debt (including Long-term Debt due within one year): OG&E Senior Notes $ 3,349.6 $ 4,182.1 $ 3,050.3 $ 3,500.4 Level 2 OG&E Industrial Authority Bonds $ 135.4 $ 135.4 $ 135.4 $ 135.4 Level 2 Tinker Debt $ 9.4 $ 10.7 $ 9.5 $ 10.0 Level 3

Stock Based Compensation (Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Stock-Based Compensation [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	The following table presents the Registrants' pre-tax compensation expense and related income tax benefit for the years ended December 31, 2020, 2019 and 2018 related to performance units and restricted stock units for the Registrants' employees. OGE Energy OG&E Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Performance units: Total shareholder return $ 7.9 $ 8.7 $ 8.2 $ 2.3 $ 3.0 $ 2.8 Earnings per share 1.0 4.3 5.1 0.3 1.5 1.8 Total performance units 8.9 13.0 13.3 2.6 4.5 4.6 Restricted stock units 0.9 0.9 0.1 0.4 0.4 — Total compensation expense $ 9.8 $ 13.9 $ 13.4 $ 3.0 $ 4.9 $ 4.6 Income tax benefit $ 2.5 $ 3.6 $ 3.4 $ 0.8 $ 1.3 $ 1.2
Performance Units Total Shareholder Return Valuation Assumptions [Table Text Block]	The following table presents the number of performance units granted based on total shareholder return and the assumptions used to calculate the grant date fair value of the performance units based on total shareholder return. OGE Energy OG&E 2020 2019 2018 2020 2019 2018 Number of units granted 201,552 208,647 261,916 67,975 68,396 91,940 Fair value of units granted $ 38.03 $ 47.00 $ 36.86 $ 38.03 $ 47.00 $ 36.86 Expected dividend yield 3.5 % 4.0 % 3.6 % 3.5 % 4.0 % 3.6 % Expected price volatility 15.0 % 17.0 % 19.0 % 15.0 % 17.0 % 19.0 % Risk-free interest rate 1.17 % 2.47 % 2.38 % 1.17 % 2.47 % 2.38 % Expected life of units (in years) 2.85 2.86 2.86 2.85 2.86 2.86
Restricted Stock Valuation Assumptions [Table Text Block]	The following table presents the number of restricted stock units granted and the grant date fair value. OGE Energy OG&E 2020 2019 2018 2020 2019 2018 Restricted stock units granted 67,193 75,929 826 22,665 26,141 — Fair value of restricted stock units granted $ 43.69 $ 41.71 $ 36.28 $ 43.69 $ 41.63 $ —
Share-based Compensation, Activity [Table Text Block]	The following tables present a summary of the activity for the Registrants' performance units and restricted stock units for the year ended December 31, 2020. OGE Energy Performance Units Restricted Total Shareholder Return Earnings Per Share (Dollars in millions) Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Units/shares outstanding at 12/31/19 664,817 155,171 72,880 Granted 201,552 (A) — 67,193 Converted (222,163) (B) $ 11.5 (74,053) (B) $ 6.6 N/A Vested N/A N/A (2,608) $ (0.1) Forfeited (31,944) (2,116) (12,546) Units/shares outstanding at 12/31/20 612,262 $ 5.4 79,002 $ 2.7 124,919 $ 4.0 Units/shares fully vested at 12/31/20 236,990 $ 5.4 79,002 $ 2.7 1,752 $ 0.1 OG&E Performance Units Restricted Total Shareholder Return Earnings Per Share (Dollars in millions) Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Units/shares outstanding at 12/31/19 227,679 53,977 25,005 Granted 67,975 (A) — 22,665 Converted (77,799) (B) $ 4.0 (25,931) (B) $ 2.3 N/A Vested N/A N/A (1,113) $ — Forfeited (28,985) (1,969) (11,100) Employee migration (6,507) (C) (842) (C) (1,327) (C) Units/shares outstanding at 12/31/20 182,363 $ 1.7 25,235 $ 0.8 34,130 $ 1.1 Units/shares fully vested at 12/31/20 75,693 $ 1.7 25,235 $ 0.8 1,114 $ — (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) These amounts represent performance units that vested at December 31, 2019 which were settled in March 2020.
Schedule of Nonvested Share Activity [Table Text Block]	The following tables present a summary of the activity for the Registrants' non-vested performance units and restricted stock units for the year ended December 31, 2020. OGE Energy Performance Units Restricted Total Shareholder Return Earnings Per Share Number Weighted-Average Number Weighted-Average Number Weighted-Average Units/shares non-vested at 12/31/19 442,654 $ 41.43 81,118 $ 31.03 72,880 $ 41.66 Granted 201,552 (A) $ 38.03 — $ — 67,193 $ 43.69 Vested (236,990) $ 36.86 (79,002) $ 31.03 (2,608) $ 40.30 Forfeited (31,944) $ 41.15 (2,116) $ 31.03 (12,546) $ 42.60 Units/shares non-vested at 12/31/20 375,272 $ 42.51 — $ — 124,919 $ 42.69 OG&E Performance Units Restricted Total Shareholder Return Earnings Per Share Number Weighted-Average Number Weighted-Average Number Weighted-Average Units/shares non-vested at 12/31/19 149,880 $ 41.31 28,046 $ 31.03 25,005 $ 41.62 Granted 67,975 (A) $ 38.03 — $ — 22,665 $ 43.69 Vested (75,693) $ 36.86 (25,235) $ 31.03 (1,113) $ 40.59 Forfeited (28,985) $ 41.12 (1,969) $ 31.03 (11,100) $ 42.60 Employee migration (6,507) (B) $ 40.26 (842) (B) $ 31.03 (1,327) (B) $ 42.76 Units/shares non-vested at 12/31/20 106,670 $ 42.49 — $ — 34,130 $ 42.67 (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target.
Fair Value of Vested Performance Units and Restricted Stock [Table Text Block]	The following table presents a summary of the Registrants' fair value for vested performance units and restricted stock units. OGE Energy OG&E Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Performance units: Total shareholder return $ 8.7 $ 9.3 $ 5.9 $ 2.8 $ 3.2 $ 2.1 Earnings per share $ 2.5 $ 5.2 $ 4.9 $ 0.8 $ 0.9 $ 1.7 Restricted stock units $ 0.1 $ 0.1 $ 0.1 $ 0.1 $ — $ —
Schedule of Unrecognized Compensation Cost, Nonvested Awards [Table Text Block]	The following table presents a summary of the Registrants' unrecognized compensation cost for non-vested performance units and restricted stock units and the weighted-average periods over which the compensation cost is expected to be recognized. OGE Energy OG&E December 31, 2020 Unrecognized Compensation Cost (In millions) Weighted Average to be Recognized (In years) Unrecognized Compensation Cost (In millions) Weighted Average to be Recognized (In years) Performance units - total shareholder return $ 7.1 1.62 $ 1.8 1.64 Restricted stock units 1.6 1.65 0.4 1.68 Total unrecognized compensation cost $ 8.7 $ 2.2

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Taxes [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The following table presents the components of income tax expense (benefit). OGE Energy OG&E Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Provision (benefit) for current income taxes: Federal $ 8.4 $ (6.4) $ (1.9) $ (3.8) $ (7.9) $ (12.4) State 0.5 5.1 (4.4) (0.6) 4.1 (4.1) Total provision (benefit) for current income taxes 8.9 (1.3) (6.3) (4.4) (3.8) (16.5) Provision (benefit) for deferred income taxes, net: Federal (105.2) 48.5 74.7 45.7 37.7 53.7 State (31.1) (17.4) 3.7 (6.6) (13.8) 2.7 Total provision (benefit) for deferred income taxes, net (136.3) 31.1 78.4 39.1 23.9 56.4 Deferred federal investment tax credits, net — — 0.1 — — 0.1 Total income tax expense (benefit) $ (127.4) $ 29.8 $ 72.2 $ 34.7 $ 20.1 $ 40.0
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following table presents a reconciliation of the statutory tax rates to the effective income tax rate. OGE Energy OG&E Year Ended December 31 2020 2019 2018 2020 2019 2018 Statutory federal tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % Impairment of OGE Energy's investment in Enable (A) 31.6 — — — — — Remeasurement of state deferred tax liabilities 0.9 (0.8) (0.4) — — — Executive compensation limitation 0.2 0.2 0.2 — — — Other 0.1 (0.7) 0.4 0.1 (0.6) (0.1) Federal renewable energy credit (B) (5.0) (6.0) (5.1) (5.4) (7.6) (6.9) Amortization of net unfunded deferred taxes (4.4) (4.5) (2.1) (4.8) (5.6) (2.9) State income taxes, net of federal income tax (1.4) (1.2) 0.4 (1.6) (1.8) (0.2) Stock-based compensation (0.3) (1.2) — — — — 401(k) dividends (0.4) (0.4) (0.3) — — — Federal deferred tax revaluation — — 0.4 — — — Effective income tax rate 42.3 % 6.4 % 14.5 % 9.3 % 5.4 % 10.9 % (A) As further discussed in Note 5, OGE Energy recorded a $780.0 million impairment on its investment in Enable in March 2020, which resulted in a tax benefit being recorded that caused a significant variance to the effective tax rate as compared to the prior year. This variance has been presented in the table as a single line item in order to facilitate comparability of other components of the effective tax rate.
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The following table presents the components of Deferred Income Taxes at December 31, 2020 and 2019. OGE Energy OG&E December 31 (In millions) 2020 2019 2020 2019 Deferred income tax liabilities, net: Accelerated depreciation and other property related differences $ 1,721.2 $ 1,656.8 $ 1,721.2 $ 1,656.8 Investment in Enable 302.6 478.2 — — Regulatory assets 52.3 28.4 52.3 28.4 Pension Plan 3.9 4.1 27.4 24.5 Bond redemption-unamortized costs 2.0 2.2 2.0 2.2 Derivative instruments 1.7 1.6 — — Federal tax credits (236.6) (238.0) (236.6) (238.0) Income taxes recoverable from customers, net (221.8) (229.9) (221.8) (229.9) State tax credits (204.4) (185.8) (189.0) (170.8) Regulatory liabilities (81.0) (68.1) (81.0) (68.1) Postretirement medical and life insurance benefits (22.4) (23.3) (15.3) (16.0) Asset retirement obligations (20.3) (19.2) (20.3) (19.2) Net operating losses (12.0) (16.6) (1.4) (5.7) Accrued liabilities (9.6) (10.7) (5.2) (4.3) Deferred federal investment tax credits (2.7) (1.8) (2.7) (1.8) Accrued vacation (2.2) (2.1) (1.6) (1.6) Other (1.4) 0.4 (6.5) (4.7) Uncollectible accounts (0.7) (0.4) (0.7) (0.4) Total deferred income tax liabilities, net $ 1,268.6 $ 1,375.8 $ 1,020.8 $ 951.4
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	The following table presents a reconciliation of the Registrants' total gross unrecognized tax benefits as of the years ended December 31, 2020, 2019 and 2018. (In millions) 2020 2019 2018 Balance at January 1 $ 20.7 $ 20.7 $ 20.7 Tax positions related to current year: Additions 1.2 — — Balance at December 31 $ 21.9 $ 20.7 $ 20.7
Summary of Tax Credit Carryforwards [Table Text Block]	The following table presents a summary of these carry forwards. OGE Energy OG&E (In millions) Carry Forward Amount Deferred Tax Asset Carry Forward Amount Deferred Tax Asset Earliest Expiration Date State operating loss $ 268.0 $ 12.0 $ 21.5 $ 1.4 2030 Federal tax credits $ 236.6 $ 236.6 $ 236.6 $ 236.6 2032 State tax credits: Oklahoma investment tax credits $ 205.6 $ 162.3 $ 186.1 $ 147.0 N/A Oklahoma capital investment board credits $ 12.7 $ 12.7 $ 12.7 $ 12.7 N/A Oklahoma zero emission tax credits $ 37.2 $ 29.3 $ 37.2 $ 29.3 2021 Louisiana inventory credits $ 0.2 $ 0.1 $ — $ — 2021 N/A - not applicable

Common Equity (Tables)

Common Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table presents the calculation of basic and diluted earnings (loss) per share for OGE Energy. (In millions except per share data) 2020 2019 2018 Net income (loss) $ (173.7) $ 433.6 $ 425.5 Average common shares outstanding: Basic average common shares outstanding 200.1 200.1 199.7 Effect of dilutive securities: Contingently issuable shares (performance and restricted stock units) — 0.6 0.8 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 Anti-dilutive shares excluded from earnings per share calculation 0.3 — —

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Long-term Debt, Unclassified [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	OG&E has tax-exempt pollution control bonds with optional redemption provisions that allow the holders to request repayment of the bonds on any business day. The following table presents information about these bonds, which can be tendered at the option of the holder during the next 12 months. Series Date Due Amount (In millions) 0.28% - 5.35% Garfield Industrial Authority, January 1, 2025 $ 47.0 0.33% - 4.31% Muskogee Industrial Authority, January 1, 2025 32.4 0.28% - 5.35% Muskogee Industrial Authority, June 1, 2027 56.0 Total (redeemable during next 12 months) $ 135.4

Short-Term Debt and Credit Fa_2

Short-Term Debt and Credit Facilities (Tables)	12 Months Ended
	Dec. 31, 2020
Short-term Debt [Abstract]
Schedule of Line of Credit Facilities [Table Text Block]	The following table presents information regarding the Registrants' revolving credit agreements at December 31, 2020. Aggregate Amount Weighted-Average Entity Commitment Outstanding (A) Interest Rate Expiration (In millions) OGE Energy (B) $ 450.0 $ 95.0 0.25 % (D) March 8, 2024 (F) OG&E (C)(E) 450.0 0.4 1.00 % (D) March 8, 2024 (F) Total $ 900.0 $ 95.4 0.25 % (A) Includes direct borrowings under the revolving credit agreements, commercial paper borrowings and letters of credit at December 31, 2020. (B) This bank facility is available to back up OGE Energy's commercial paper borrowings and to provide revolving credit borrowings. This bank facility can also be used as a letter of credit facility. (C) This bank facility is available to back up OG&E's commercial paper borrowings and to provide revolving credit borrowings. This bank facility can also be used as a letter of credit facility. (D) Represents the weighted-average interest rate for the outstanding borrowings under the revolving credit agreements, commercial paper borrowings and letters of credit. (E) OG&E has an intercompany borrowing agreement with OGE Energy whereby OG&E has access to up to $350.0 million of OGE Energy's revolving credit amount. This agreement has a termination date of March 8, 2024. At December 31, 2020, there were no intercompany borrowings under this agreement. (F) In March 2017, the Registrants entered into unsecured five-year revolving credit agreements totaling $900.0 million ($450.0 million for OGE Energy and $450.0 million for OG&E). Each of the revolving credit facilities contained an option, which could be exercised up to two times, to extend the term of the respective facility for an additional year. In March 2018, the Registrants each utilized one of those extensions to extend the maturity of their respective credit facility from March 8, 2022 to March 8, 2023. In January 2021, the Registrants each utilized the second of those extensions to extend the maturity of their respective credit facility from March 8, 2023 to March 8, 2024. Commitments of a single existing lender with respect to $50.0 million of OGE Energy's credit facility, however, were not extended and, unless the non-extending lender is replaced in accordance with the terms of the credit facility, such commitments will expire March 8, 2023. The non-extending lender is not party to the OG&E facility.

Retirement Plans and Postreti_2

Retirement Plans and Postretirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Plans and Postretirement Benefit Plans [Abstract]
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	These amounts have been recorded in Accrued Benefit Obligations with the offset in Accumulated Other Comprehensive Loss (except OG&E's portion, which is recorded as a regulatory asset as discussed in Note 1) in the balance sheets. The amounts in Accumulated Other Comprehensive Loss and those recorded as a regulatory asset represent a net periodic benefit cost to be recognized in the statements of income in future periods. The benefit obligation for OGE Energy's Pension Plan and the Restoration of Retirement Income Plan represents the projected benefit obligation, while the benefit obligation for the postretirement benefit plans represents the accumulated postretirement benefit obligation. The accumulated postretirement benefit obligation for OGE Energy's Pension Plan and Restoration of Retirement Income Plan differs from the projected benefit obligation in that the former includes no assumption about future compensation levels. OGE Energy OG&E Pension Plan Restoration of Retirement Pension Plan Restoration of Retirement December 31 (In millions) 2020 2019 2020 2019 2020 2019 2020 2019 Change in benefit obligation Beginning obligations $ 616.1 $ 615.9 $ 10.3 $ 9.6 $ 462.0 $ 453.6 $ 6.1 $ 6.0 Service cost 13.2 12.9 0.8 0.5 9.2 9.0 0.1 0.2 Interest cost 17.0 20.7 0.2 0.4 12.6 15.6 0.1 0.2 Plan settlements (42.8) (83.1) (5.3) (1.2) (33.5) (45.6) (4.5) (0.9) Plan amendments — — — 0.3 — — — — Plan curtailments — — 0.2 — — — — — Special termination benefits 7.6 — — — 5.1 — — — Actuarial losses 57.7 64.3 1.6 0.7 41.0 42.1 1.2 0.6 Benefits paid (14.2) (14.6) — — (12.3) (12.7) — — Ending obligations $ 654.6 $ 616.1 $ 7.8 $ 10.3 $ 484.1 $ 462.0 $ 3.0 $ 6.1 Change in plans' assets Beginning fair value $ 530.3 $ 522.8 $ — $ — $ 399.1 $ 387.6 $ — $ — Actual return on plans' assets 77.0 85.2 — — 57.0 64.8 — — Employer contributions 20.0 20.0 5.3 1.2 10.0 5.0 4.5 0.9 Plan settlements (42.8) (83.1) (5.3) (1.2) (33.5) (45.6) (4.5) (0.9) Benefits paid (14.2) (14.6) — — (12.3) (12.7) — — Ending fair value $ 570.3 $ 530.3 $ — $ — $ 420.3 $ 399.1 $ — $ — Funded status at end of year $ (84.3) $ (85.8) $ (7.8) $ (10.3) $ (63.8) $ (62.9) $ (3.0) $ (6.1) Accumulated postretirement benefit obligation $ 610.8 $ 563.3 $ 6.9 $ 8.1 $ 454.7 $ 425.8 $ 2.9 $ 4.8 For the year ended December 31, 2020, Pension Plan actuarial losses were primarily due to movement in the discount rate, special termination benefits due to a voluntary retirement program offered by OGE Energy and more retirements and terminations than expected which are expected to accelerate lump sum payments in 2021. These losses were partially offset by gains from lowering the interest crediting rate and plan mortality assumptions. OGE Energy OG&E Postretirement Benefit Plans Postretirement Benefit Plans December 31 (In millions) 2020 2019 2020 2019 Change in benefit obligation Beginning obligations $ 136.5 $ 135.8 $ 104.7 $ 104.8 Service cost 0.2 0.2 0.2 0.2 Interest cost 4.2 5.6 3.2 4.3 Plan curtailments 4.0 — 3.1 — Participants' contributions 3.3 4.1 2.4 3.0 Actuarial losses 7.3 2.9 4.5 2.2 Benefits paid (11.0) (12.1) (8.6) (9.8) Ending obligations $ 144.5 $ 136.5 $ 109.5 $ 104.7 Change in plans' assets Beginning fair value $ 47.0 $ 45.3 $ 41.9 $ 40.6 Actual return on plans' assets 1.2 4.6 1.1 4.0 Employer contributions 7.1 5.1 5.9 4.1 Participants' contributions 3.3 4.1 2.4 3.0 Benefits paid (11.0) (12.1) (8.6) (9.8) Ending fair value $ 47.6 $ 47.0 $ 42.7 $ 41.9 Funded status at end of year $ (96.9) $ (89.5) $ (66.8) $ (62.8)
Schedule of Defined Benefit Plans Disclosures [Table Text Block]	The following tables present the net periodic benefit cost components, before consideration of capitalized amounts, of OGE Energy's Pension Plan, Restoration of Retirement Income Plan and postretirement benefit plans that are included in the financial statements. Service cost is presented within Other Operation and Maintenance, and the remaining net period benefit cost components as listed in the following tables are presented within Other Net Periodic Benefit Income (Expense) in the statements of income. OG&E recovers specific amounts of pension and postretirement medical costs in rates approved in its Oklahoma rate reviews. In accordance with approved orders, OG&E defers the difference between actual pension and postretirement medical expenses and the amount approved in its last Oklahoma rate review as a regulatory asset or regulatory liability. These amounts have been recorded in the Pension tracker in the regulatory assets and liabilities table in Note 1 and within Other Net Periodic Benefit Income (Expense) in the statements of income. OGE Energy OG&E Pension Plan Restoration of Retirement Pension Plan Restoration of Retirement Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 2020 2019 2018 2020 2019 2018 Service cost $ 13.2 $ 12.9 $ 14.9 $ 0.8 $ 0.5 $ 0.4 $ 9.2 $ 9.0 $ 9.8 $ 0.1 $ 0.2 $ 0.2 Interest cost 17.0 20.7 23.8 0.2 0.4 0.3 12.6 15.6 17.6 0.1 0.2 0.2 Expected return on plan assets (37.6) (36.1) (44.1) — — — (27.9) (27.6) (33.1) — — — Amortization of net loss 17.1 17.3 16.2 0.5 0.5 0.7 12.1 12.9 12.1 0.4 0.3 0.5 Plan curtailments — — — 0.2 — — — — — — — — Special termination benefits 7.6 — — — — — 5.1 — — — — — Amortization of unrecognized prior service cost (A) — — — — — 0.1 — — — — — — Settlement cost 14.1 27.6 25.1 2.7 0.5 1.0 11.4 16.4 19.4 2.4 0.5 0.4 Total net periodic benefit cost 31.4 42.4 35.9 4.4 1.9 2.5 22.5 26.3 25.8 3.0 1.2 1.3 Less: Amount paid by unconsolidated affiliates (B) 2.0 2.9 2.5 0.1 0.1 0.1 Plus: Amount allocated from OGE Energy (B) 5.9 4.5 5.7 1.3 0.5 1.2 Net periodic benefit cost $ 29.4 $ 39.5 $ 33.4 $ 4.3 $ 1.8 $ 2.4 $ 28.4 $ 30.8 $ 31.5 $ 4.3 $ 1.7 $ 2.5 (A) Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment. (B) "Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E. In addition to the net periodic benefit cost amounts recognized, as presented in the table above, for the Pension and Restoration of Retirement Income Plans in 2020, 2019 and 2018, the Registrants recognized the following: Year Ended December 31 (In millions) 2020 2019 2018 Decrease of pension expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ (13.8) $ (16.1) $ (14.1) Deferral of pension expense related to pension settlement, curtailment and special termination benefits charges: Oklahoma jurisdiction (A) $ 21.6 $ 17.9 $ 22.1 Arkansas jurisdiction (A) $ 2.0 $ 1.7 $ 2.1 (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1. OGE Energy OG&E Postretirement Benefit Plans Postretirement Benefit Plans Year Ended December 31 (In millions) 2020 2019 2018 2020 2019 2018 Service cost $ 0.2 $ 0.2 $ 0.3 $ 0.2 $ 0.2 $ 0.2 Interest cost 4.2 5.6 5.4 3.2 4.3 4.2 Expected return on plan assets (1.8) (1.9) (2.0) (1.7) (1.7) (1.8) Amortization of net loss 2.0 2.0 3.8 2.1 2.1 3.8 Plan curtailments 1.5 — — 1.3 — — Amortization of unrecognized prior service cost (A) (8.4) (8.4) (8.4) (6.1) (6.1) (6.1) Total net periodic benefit cost (2.3) (2.5) (0.9) (1.0) (1.2) 0.3 Less: Amount paid by unconsolidated affiliates (B) (0.7) (0.6) (0.5) Plus: Amount allocated from OGE Energy (B) (0.5) (0.6) (0.7) Net periodic benefit cost $ (1.6) $ (1.9) $ (0.4) $ (1.5) $ (1.8) $ (0.4) (A) Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment. (B) "Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E. In addition to the net periodic benefit income amounts recognized, as presented in the table above, for the postretirement benefit plans in 2020, 2019 and 2018, the Registrants recognized the following: Year Ended December 31 (In millions) 2020 2019 2018 Increase of postretirement expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ 0.2 $ 1.0 $ 4.4 Deferral of postretirement expense related to postretirement plan curtailment charges: Oklahoma jurisdiction (A) $ 1.4 $ — $ — Arkansas jurisdiction (A) $ 0.1 $ — $ —
Schedule of Capitalized Pension and Postretirement Cost [Table Text Block]	OGE Energy OG&E (In millions) 2020 2019 2018 2020 2019 2018 Capitalized portion of net periodic pension benefit cost $ 3.8 $ 3.6 $ 3.8 $ 3.1 $ 3.0 $ 3.2 Capitalized portion of net periodic postretirement benefit cost $ 0.2 $ 0.2 $ 0.2 $ 0.1 $ 0.1 $ 0.1
Schedule of Assumptions Used [Table Text Block]	Rate Assumptions Pension Plan and Postretirement Year Ended December 31 2020 2019 2018 2020 2019 2018 Assumptions to determine benefit obligations: Discount rate 2.30 % 3.15 % 4.20 % 2.45 % 3.25 % 4.30 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A N/A Interest crediting rate 3.50 % 4.00 % 4.00 % N/A N/A N/A Assumptions to determine net periodic benefit cost: Discount rate 2.88 % 3.63 % 3.73 % 3.25 % 4.30 % 3.70 % Expected return on plan assets 7.50 % 7.50 % 7.50 % 4.00 % 4.00 % 4.00 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A N/A Interest crediting rate 4.00 % 4.00 % 4.00 % N/A N/A N/A
Projected Benefit Obligation Funded Status Thresholds [Table Text Block]	The Pension Plan assets are held in a trust which follows an investment policy and strategy designed to reduce the funded status volatility of the Plan by utilizing liability driven investing. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The investment policy follows a glide path approach that shifts a higher portfolio weighting to fixed income as the Plan's funded status increases. The following table presents the targeted fixed income and equity allocations at different funded status levels. Projected Benefit Obligation Funded Status Thresholds <90% 95% 100% 105% 110% 115% 120% Fixed income 50% 58% 65% 73% 80% 85% 90% Equity 50% 42% 35% 27% 20% 15% 10% Total 100% 100% 100% 100% 100% 100% 100%
Pension Plan Equity Asset Allocation Table [Table Text Block]	Within the portfolio's overall allocation to equities, the funds are allocated according to the guidelines in the following table. Asset Class Target Allocation Minimum Maximum Domestic Large Cap Equity 40% 35% 60% Domestic Mid-Cap Equity 15% 5% 25% Domestic Small-Cap Equity 25% 5% 30% International Equity 20% 10% 30%
Schedule of Allocation of Plan Assets [Table Text Block]	The following tables present the postretirement benefit plans' investments that are measured at fair value on a recurring basis at December 31, 2020 and 2019. There were no Level 2 investments held by the postretirement benefit plans at December 31, 2020 and 2019. (In millions) December 31, 2020 Level 1 Level 3 Group retiree medical insurance contract $ 33.4 $ — $ 33.4 Mutual fund 10.8 10.8 — Money market fund 3.4 3.4 — Total OGE Energy plan investments $ 47.6 $ 14.2 $ 33.4 Plan investments attributable to affiliates (4.9) Total OG&E plan investments $ 42.7 (In millions) December 31, 2019 Level 1 Level 3 Group retiree medical insurance contract $ 34.8 $ — $ 34.8 Mutual funds 10.9 10.9 — Money market fund 1.2 1.2 — Total OGE Energy plan investments $ 46.9 $ 12.1 $ 34.8 Plan investments attributable to affiliates (5.0) Total OG&E plan investments $ 41.9
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block]	The following table presents a reconciliation of the postretirement benefit plans' investments that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Year Ended December 31 (In millions) 2020 Group retiree medical insurance contract: Beginning balance $ 34.8 Claims paid (3.7) Investment fees (0.1) Interest income 0.8 Net unrealized gains related to instruments held at the reporting date 0.6 Dividend income 0.6 Realized gains 0.4 Ending balance $ 33.4
Schedule of Expected Benefit Payments [Table Text Block]	The following table presents the benefit payments the Registrants expect to pay related to the Pension Plan and Restoration of Retirement Income Plan. These expected benefits are based on the same assumptions used to measure OGE Energy's benefit obligation at the end of the year and include benefits attributable to estimated future employee service. (In millions) OGE Energy OG&E 2021 $ 164.2 $ 123.9 2022 $ 43.3 $ 33.1 2023 $ 42.5 $ 31.9 2024 $ 44.2 $ 32.3 2025 $ 41.1 $ 29.3 After 2025 $ 203.6 $ 141.1 The Medicare Prescription Drug, Improvement and Modernization Act of 2003 expanded coverage for prescription drugs. The following table presents the gross benefit payments the Registrants expect to pay related to the postretirement benefit plans, including prescription drug benefits. (In millions) OGE Energy OG&E 2021 $ 11.9 $ 9.4 2022 $ 11.8 $ 9.3 2023 $ 11.4 $ 8.9 2024 $ 10.0 $ 7.7 2025 $ 9.5 $ 7.3 After 2025 $ 40.9 $ 31.0
Defined Benefit Plan, Plan Assets, Category	The following tables present the Pension Plan's investments that are measured at fair value on a recurring basis at December 31, 2020 and 2019. There were no Level 3 investments held by the Pension Plan at December 31, 2020 and 2019. (In millions) December 31, 2020 Level 1 Level 2 Net Asset Value (A) Common stocks $ 252.3 $ 252.3 $ — $ — U.S. Treasury notes and bonds (B) 134.3 134.3 — — Mortgage- and asset-backed securities 29.3 — 29.3 — Corporate fixed income and other securities 116.6 — 116.6 — Commingled fund (C) 25.4 — — 25.4 Foreign government bonds 4.6 — 4.6 — U.S. municipal bonds 1.8 — 1.8 — Money market fund 8.8 — — 8.8 Mutual fund 9.2 9.2 — — Preferred stocks 0.6 0.6 — — U.S. Treasury futures: Cash collateral 0.7 0.7 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 583.7 $ 397.1 $ 152.4 $ 34.2 Receivable from broker for securities sold 0.2 Interest and dividends receivable 2.2 Payable to broker for securities purchased (15.8) Total OGE Energy Pension Plan assets $ 570.3 Pension Plan investments attributable to affiliates (150.0) Total OG&E Pension Plan assets $ 420.3 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. (In millions) December 31, 2019 Level 1 Level 2 Net Asset Value (A) Common stocks $ 202.0 $ 202.0 $ — $ — U.S. Treasury notes and bonds (B) 134.8 134.8 — — Mortgage- and asset-backed securities 45.8 — 45.8 — Corporate fixed income and other securities 130.5 — 130.5 — Commingled fund (C) 23.9 — — 23.9 Foreign government bonds 3.0 — 3.0 — U.S. municipal bonds 1.1 — 1.1 — Money market fund 2.4 — — 2.4 Mutual fund 7.5 7.5 — — Preferred stocks 0.7 0.7 — — Futures: U.S. Treasury futures (receivable) 22.9 — 22.9 — U.S. Treasury futures (payable) (10.9) — (10.9) — Cash collateral 0.6 0.6 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 564.4 $ 345.6 $ 192.5 $ 26.3 Interest and dividends receivable 2.4 Payable to broker for securities purchased (36.5) Total OGE Energy Pension Plan assets $ 530.3 Pension Plan investments attributable to affiliates (131.2) Total OG&E Pension Plan assets $ 399.1 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher.

Report of Business Segments (Ta

Report of Business Segments (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	The following tables present the results of OGE Energy's business segments for the years ended December 31, 2020, 2019 and 2018. 2020 Electric Utility Natural Gas Midstream Operations Other Eliminations Total (In millions) Operating revenues $ 2,122.3 $ — $ — $ — $ 2,122.3 Cost of sales 644.6 — — — 644.6 Other operation and maintenance 464.4 1.7 (3.3) — 462.8 Depreciation and amortization 391.3 — — — 391.3 Taxes other than income 97.2 0.4 3.8 — 101.4 Operating income (loss) 524.8 (2.1) (0.5) — 522.2 Equity in losses of unconsolidated affiliates (A) — (668.0) — — (668.0) Other income (expense) 4.1 (2.9) 3.6 (1.6) 3.2 Interest expense 154.8 — 5.3 (1.6) 158.5 Income tax expense (benefit) 34.7 (158.0) (4.1) — (127.4) Net income (loss) $ 339.4 $ (515.0) $ 1.9 $ — $ (173.7) Investment in unconsolidated affiliates $ — $ 374.3 $ 23.1 $ — $ 397.4 Total assets $ 10,489.0 $ 378.1 $ 116.4 $ (264.7) $ 10,718.8 Capital expenditures $ 650.5 $ — $ — $ — $ 650.5 (A) In March 2020, OGE Energy recorded a $780.0 million impairment on its investment in Enable, as further discussed in Notes 5 and 7. 2019 Electric Utility Natural Gas Midstream Operations Other Eliminations Total (In millions) Operating revenues $ 2,231.6 $ — $ — $ — $ 2,231.6 Cost of sales 786.9 — — — 786.9 Other operation and maintenance 492.5 2.8 (3.5) — 491.8 Depreciation and amortization 355.0 — — — 355.0 Taxes other than income 89.5 0.4 3.7 — 93.6 Operating income (loss) 507.7 (3.2) (0.2) — 504.3 Equity in earnings of unconsolidated affiliates — 113.9 — — 113.9 Other income (expense) 3.1 (8.6) 2.2 (3.6) (6.9) Interest expense 140.5 — 11.0 (3.6) 147.9 Income tax expense (benefit) 20.1 20.7 (11.0) — 29.8 Net income $ 350.2 $ 81.4 $ 2.0 $ — $ 433.6 Investment in unconsolidated affiliates $ — $ 1,132.9 $ 18.6 $ — $ 1,151.5 Total assets $ 10,076.6 $ 1,135.4 $ 107.0 $ (294.7) $ 11,024.3 Capital expenditures $ 635.5 $ — $ — $ — $ 635.5 2018 Electric Utility Natural Gas Midstream Operations Other Eliminations Total (In millions) Operating revenues $ 2,270.3 $ — $ — $ — $ 2,270.3 Cost of sales 892.5 — — — 892.5 Other operation and maintenance 473.8 1.4 (0.6) — 474.6 Depreciation and amortization 321.6 — — — 321.6 Taxes other than income 88.2 0.6 3.2 — 92.0 Operating income (loss) 494.2 (2.0) (2.6) — 489.6 Equity in earnings of unconsolidated affiliates — 152.8 — — 152.8 Other income (expense) 25.6 (4.9) (3.4) (6.0) 11.3 Interest expense 151.8 — 10.2 (6.0) 156.0 Income tax expense (benefit) 40.0 37.1 (4.9) — 72.2 Net income (loss) $ 328.0 $ 108.8 $ (11.3) $ — $ 425.5 Investment in unconsolidated affiliates $ — $ 1,166.6 $ 10.9 $ — $ 1,177.5 Total assets $ 9,704.5 $ 1,169.8 $ 184.8 $ (310.5) $ 10,748.6 Capital expenditures $ 573.6 $ — $ — $ — $ 573.6

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Unrecorded Unconditional Purchase Obligations Disclosure [Table Text Block]	The following table presents the Registrants' future purchase obligations and commitments estimated for the next five years. (In millions) 2021 2022 2023 2024 2025 Total Purchase obligations and commitments: Minimum purchase commitments $ 72.5 $ 50.4 $ 50.4 $ 36.7 $ 25.9 $ 235.9 Expected wind purchase commitments 55.2 55.6 56.0 56.6 56.9 280.3 Long-term service agreement commitments 2.4 2.4 7.9 35.1 31.2 79.0 Total purchase obligations and commitments $ 130.1 $ 108.4 $ 114.3 $ 128.4 $ 114.0 $ 595.2
Schedule of Wind Power Purchases [Table Text Block]	The following table presents OG&E's wind power purchase contracts. Company Location Original Term of Contract Expiration of Contract MWs CPV Keenan Woodward County, OK 20 years 2030 152.0 Edison Mission Energy Dewey County, OK 20 years 2031 130.0 NextEra Energy Blackwell, OK 20 years 2032 60.0 The following table presents a summary of OG&E's wind power purchases for the years ended December 31, 2020, 2019 and 2018. Year Ended December 31 (In millions) 2020 2019 2018 CPV Keenan $ 27.5 $ 27.2 $ 27.0 Edison Mission Energy 22.8 23.1 21.7 NextEra Energy 7.0 7.4 6.8 FPL Energy (A) — — 2.1 Total wind power purchased $ 57.3 $ 57.7 $ 57.6

Schedule II (Tables)

Schedule II (Tables)	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II Valuation and Qualifying Accounts [Table Text Block]	SCHEDULE II - Valuation and Qualifying Accounts Additions Description Balance at Beginning of Period Charged to Costs and Expenses Deductions (A) Balance at End of Period (In millions) Balance at December 31, 2018 Reserve for Uncollectible Accounts $ 1.5 $ 3.4 $ 3.2 $ 1.7 Balance at December 31, 2019 Reserve for Uncollectible Accounts $ 1.7 $ 2.2 $ 2.4 $ 1.5 Balance at December 31, 2020 Reserve for Uncollectible Accounts $ 1.5 $ 3.0 $ 1.9 $ 2.6

Summary of Significant Accoun_4

Summary of Significant Accounting Policies Regulated Operations (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Schedule of Regulatory Assets and Liabilities [Line Items]
Fuel clause under recoveries		$ 0	$ 39.5
Fuel clause over recoveries		28.6	4.8
Regulatory Assets, Current		19.8	48.7
Regulatory Assets, Noncurrent		415.6	306
Regulatory Liability, Current		35.1	29
Regulatory Liability, Noncurrent		$ 1,188.9	1,223.5
CenterPoint [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Percentage Share of Management Rights		50.00%
OGE Energy [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Percentage Share of Management Rights		50.00%
SPP Cost Tracker Rider Over Recovery [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	[1]	$ 0	2.6
Reserve for Tax Refund [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	[1]	0.8	12.7
Income taxes recoverable from customers, net [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Noncurrent		867.4	899.2
Accrued removal obligations [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Noncurrent		316.8	318.5
Other Regulatory Liabilities [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	[1]	4.2	6.9
Regulatory Liability, Noncurrent		4.7	5.8
Oklahoma demand program rider over recovery
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	[1]	1.5	2
SPP cost tracker under recovery [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	[2]	7	0
Benefit obligations regulatory asset [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		164.9	167.2
Deferred storm expenses [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		158.8	65.5
Smart Grid [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		11.2	18.4
Unamortized loss on reacquired debt [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		9.7	10.6
Deferred Pension Expenses [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		9.3	8
Dry Scrubber Regulatory Asset [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		19.7	20.6
Other Regulatory Assets [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	[2]	8.4	5.5
Regulatory Assets, Noncurrent		11.1	13.4
Pension tracker [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		18.1	2.3
Frontier Plant
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		6.4	0
COVID-19 Impact
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		6.4	0
Generation Capacity Replacement rider
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	[2]	$ 4.4	$ 3.7
[1]	Included in Other Current Liabilities in the balance sheets.
[2]	Included in Other Current Assets in the balance sheets.

Summary of Significant Accoun_5

Summary of Significant Accounting Policies Accounting Records (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory Assets, Current	$ 19.8	$ 48.7
Regulatory Assets, Noncurrent	415.6	306
Deferred Storm and Property Reserve Deficiency, Current	2.7
Regulatory Liability, Current	35.1	29
Pension Plans, Defined Benefit [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset	147.3	160.5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset	26.2	23.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | Prior Service Cost [Member]
Components of Benefit Obligation Regulatory Asset	$ (8.6)	$ (16.6)

Summary of Significant Accoun_6

Summary of Significant Accounting Policies Allowance for Uncollectible Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Allowance for Doubtful Accounts Receivable	$ 2.6	$ 1.5

Summary of Significant Accoun_7

Summary of Significant Accounting Policies Fuel Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other	$ 41.2	$ 24.4
OG&E [Member]
Fuel inventories	36.5	46.3
Other	36.9	19.6
Public Utilities, Inventory, Fuel [Member]
Fuel inventories	$ 36.5	$ 46.3

Summary of Significant Accoun_8

Summary of Significant Accounting Policies Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 13,442.2		$ 12,912.7
Accumulated Depreciation	4,067.6		3,868.1
Net property, plant and equipment	9,374.6		9,044.6
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments, Related Accumulated Depreciation	$ 67.3		$ 61.8
McClain Plant [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	77.00%	[1]	77.00%	[2]
Property, Plant and Equipment, Gross	$ 257.1	[1]	$ 254.4	[2]
Accumulated Depreciation	96	[1]	83.5	[2]
Net property, plant and equipment	161.1	[1]	170.9	[2]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0.1		$ 0.2
Redbud Plant [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	51.00%	[1],[3]	51.00%	[2],[4]
Property, Plant and Equipment, Gross	$ 531.8	[1],[3]	$ 529.9	[2],[4]
Accumulated Depreciation	181.9	[1],[3]	159	[2],[4]
Net property, plant and equipment	349.9	[1],[3]	370.9	[2],[4]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	1.8		1.4
Amount of Acquisition Adjustments	148.3		148.3
OGE Energy [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	6.1		6.1
Accumulated Depreciation	0		0
Net property, plant and equipment	6.1		6.1
OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	13,436.1		12,906.6
Accumulated Depreciation	4,067.6		3,868.1
Net property, plant and equipment	9,368.5		9,038.5
Capitalized Computer Software, Gross	89.7		71.3
Capitalized Computer Software, Amortization	14.9		11		$ 9.6
OG&E [Member] | Total Property Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	13,436.1		12,906.6
Accumulated Depreciation	4,067.6		3,868.1
Net property, plant and equipment	9,368.5		9,038.5
OG&E [Member] | Electric Transmission and Distribution [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,809.9		4,468.6
Accumulated Depreciation	1,422.1		1,381.1
Net property, plant and equipment	3,387.8		3,087.5
OG&E [Member] | Electric Generation Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,932.2	[5]	4,838.6	[6]
Accumulated Depreciation	1,713.6	[5]	1,601	[6]
Net property, plant and equipment	3,218.6	[5]	3,237.6	[6]
Amount of Acquisition Adjustments	148.3		148.3
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments, Related Accumulated Depreciation	67.3		61.8
OG&E [Member] | Electric Transmission [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,944.6	[7]	2,901.1	[8]
Accumulated Depreciation	591.7	[7]	565.5	[8]
Net property, plant and equipment	2,352.9	[7]	2,335.6	[8]
Amount of Acquisition Adjustments	3.3		3.3
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments, Related Accumulated Depreciation	0.9		0.8
OG&E [Member] | Finite-Lived Intangible Assets, Major Class Name [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	254.1		225.2
Accumulated Depreciation	153.9		145.4
Net property, plant and equipment	100.2		79.8
OG&E [Member] | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	495.3		473.1
Accumulated Depreciation	186.3		175.1
Net property, plant and equipment	$ 309		$ 298
[1]	Construction work in progress was $0.1 million and $1.8 million for the McClain and Redbud Plants, respectively.
[2]	Construction work in progress was $0.2 million and $1.4 million for the McClain and Redbud Plants, respectively.
[3]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $67.3 million.
[4]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million.
[5]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $67.3 million.
[6]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million.
[7]	This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.9 million.
[8]	This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.8 million.

Summary of Significant Accoun_9

Summary of Significant Accounting Policies Depreciation and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Provision for Depreciation Rate	2.60%	2.70%
Projected provision for depreciation in next fiscal year	2.60%
Percent Of Intangible Plant Balance Amortizable	99.00%
Percent of Intangible Plant Balance Amortizable Thereafter	1.00%
Transmission Equipment [Member] | OG&E [Member]
Amount of Acquisition Adjustments	$ 3.3
Redbud Plant [Member]
Amount of Acquisition Adjustments	$ 148.3	$ 148.3

Summary of Significant Accou_10

Summary of Significant Accounting Policies Asset Retirement Obligation (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at January 1		$ 73.5	$ 83.9
Accretion expense		0.5	1
Revisions in estimated cash flows	[1]	5.8	(2.4)
Liabilities settled	[2]	(0.2)	(9)
Balance at December 31		$ 79.6	$ 73.5
[1]	Assumptions changed related to the estimated timing and estimated cost of the removal of asbestos at OG&E's generating facilities.
[2]	Asset retirement obligations were settled for asbestos removal at one of OG&E's generating facilities

Summary of Significant Accou_11

Summary of Significant Accounting Policies Enviromental Costs (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accrued Environmental Loss Contingencies, Noncurrent	$ 25	$ 18.7

Summary of Significant Accou_12

Summary of Significant Accounting Policies Allowance for Funds Used During Construction (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Public Utilities, Allowance for Funds Used During Construction, Rate	7.30%	7.60%	7.60%

Summary of Significant Accou_13

Summary of Significant Accounting Policies Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive (income) loss		$ (32.1)	$ (27.9)	$ (28.9)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(8.2)	(9.1)
Amounts reclassified from accumulated other comprehensive income (loss)		(3.9)	(3.4)	(3.3)
Amounts reclassified from accumulated other comprehensive income (loss)		2.1	1.5
Amounts Reclassified from Accumulated OCI, Net of Tax and Noncontrolling Interest		4	10.1
Other Comprehensive Income (Loss), Net of Tax		(4.2)	1	(5.7)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		2.2	8.6	4.7
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)		(6.1)	(12)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	(5.1)	(4.5)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	[1]	(2.9)	(11.3)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		(8)	(15.8)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		(1.9)	(3.8)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss)		2.1	1.9
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	0.1	0.2
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	[1]	2.3	2.3
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	[1]	0.4	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		2.8	2.5
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		0.7	0.6
Defined Benefit Plans Income Loss [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive income (loss)		(34.1)	(35.1)	(38.8)
Other comprehensive income before reclassifications		(5.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(8.3)
Amounts reclassified from accumulated other comprehensive income (loss)		3.9	3.4
Other Comprehensive Income (Loss), Net of Tax		1	3.7
Defined Benefit Plans Income Loss [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive income (loss)		1.4	4.2	4.6
Other comprehensive income before reclassifications		(2.4)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(0.2)
Amounts reclassified from accumulated other comprehensive income (loss)		(0.1)	(0.2)
Other Comprehensive Income (Loss), Net of Tax		(2.8)	(0.4)
AOCI Attributable to Parent [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Net of Tax		(4.2)	1	(5.7)
Defined Benefit Plan Prior Service Cost [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive income (loss)		1.9	3.6	5.3
Other comprehensive income before reclassifications		0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0
Amounts reclassified from accumulated other comprehensive income (loss)		(1.7)	(1.7)
Other Comprehensive Income (Loss), Net of Tax		(1.7)	(1.7)
Settlement Cost [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		2.2	8.6
Settlement Cost [Member] | Defined Benefit Plans Income Loss [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		0	0
Settlement Cost [Member] | Defined Benefit Plan Prior Service Cost [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		2.2	8.6
Settlement Cost [Member] | Defined Benefit Plan Prior Service Cost [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		0	0
Curtailment
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		(0.3)
Curtailment | Defined Benefit Plans Income Loss [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		0
Curtailment | Defined Benefit Plans Income Loss [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		(0.3)
Curtailment | Defined Benefit Plan Prior Service Cost [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		0
Commodity Contract [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent			(0.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(0.7)
Amounts reclassified from accumulated other comprehensive income (loss)		0	0
Net current period other comprehensive income (loss)		(0.7)	(0.6)
AOCI, Derivative Qualifying as Hedge, Excluded Component, after Tax		(1.3)	(0.6)	$ 0
Commodity Contract [Member] | Settlement Cost [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		0	$ 0
Commodity Contract [Member] | Curtailment
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax		$ 0
[1]	These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost (see Note 13 for additional information).

Revenue from Contracts with C_3

Revenue from Contracts with Customers (Details) - USD ($) $ 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
Provision for Rate Refund [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	3.8	(0.9)	(6)
Integrated Market [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	49.6	38.4	48.7
Transmission [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	143.3	148	147.4
Other Contracts with Customers [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	30.7	29.1	27.1
Residential [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	842.7	865.8	877.8
Commercial [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	465.6	486.6	500
Industrial [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	192.6	217.8	228.9
Oilfield [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	169.2	200.4	190.4
Public Authority [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	172.3	190.3	197.4
Total Retail Customer [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,842.4	$ 1,960.9	$ 1,994.5

Leases, Codification Topic 84_2

Leases, Codification Topic 842 (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Lessee, Operating Lease, Contingent Liability		$ 6.8
Operating Lease, Cost		6.4	$ 6	$ 4.9
Operating Leased Assets [Line Items]
Cash Paid on Operating Leases		6.4	5.6
Operating Lease, Right-of-Use Asset	[1]	37.6	40.9
Operating Lease, Liability	[2]	$ 42.3	$ 45.8
Operating Lease, Weighted Average Remaining Lease Term		12 years 6 months	13 years 1 month 6 days
Operating Lease, Weighted Average Discount Rate, Percent		3.90%	3.90%
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		$ 1.4	$ 10.7
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months		6.3
Lessee, Operating Lease, Liability, Payments, Due Year Two		5.7
Lessee, Operating Lease, Liability, Payments, Due Year Three		5.1
Lessee, Operating Lease, Liability, Payments, Due Year Four		3.2
Lessee, Operating Lease, Liability, Payments, Due Year Five		3
Lessee, Operating Lease, Liability, Payments, Due after Year Five		31.7
Lessee, Operating Lease, Liability, Payments, Due		55
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		12.7
Lessee, Operating Lease, Contingent Liability		6.8
Operating Lease, Cost		6.4	6	4.9
Og and E [Member]
Leases [Abstract]
Operating Lease, Cost		5.5	5.1	4.1
Operating Leased Assets [Line Items]
Cash Paid on Operating Leases		5.5	4.8
Operating Lease, Right-of-Use Asset	[1]	37	39.6
Operating Lease, Liability	[2]	$ 41.7	$ 44.3
Operating Lease, Weighted Average Remaining Lease Term		12 years 8 months 12 days	13 years 6 months
Operating Lease, Weighted Average Discount Rate, Percent		3.90%	3.90%
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		$ 1.4	$ 10.7
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months		5.7
Lessee, Operating Lease, Liability, Payments, Due Year Two		5.7
Lessee, Operating Lease, Liability, Payments, Due Year Three		5.1
Lessee, Operating Lease, Liability, Payments, Due Year Four		3.2
Lessee, Operating Lease, Liability, Payments, Due Year Five		3
Lessee, Operating Lease, Liability, Payments, Due after Year Five		31.7
Lessee, Operating Lease, Liability, Payments, Due		54.4
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		12.7
Operating Lease, Cost		$ 5.5	$ 5.1	$ 4.1
[1]	Included in Property, Plant and Equipment in the Registrants' balance sheets.
[2]	Included in Other Deferred Credits and Other Liabilities in the Registrants' balance sheets.

Investment in Unconsolidated _3

Investment in Unconsolidated Affiliate (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	May 01, 2013
Schedule of Equity Method Investments [Line Items]
Limited Partner Units Owned		111
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		25.50%		25.50%	25.60%
Distribution Made to Limited Partner, Distributions Declared, Per Unit		$ 0.16525
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		$ 1,332.3		$ 652.5
Equity in earnings (losses) of unconsolidated affiliates	[1]	(668)	[2]	113.9	$ 152.8
Share Price						$ 30.36
Enable Midstream Partners [Member]
Schedule of Equity Method Investments [Line Items]
Distributions received		$ 91.7		144	141.2
Share Price		$ 5.26
Enogex LLC [Member]
Schedule of Equity Method Investments [Line Items]
Increase in fair value of net assets							$ 2,200
OGE Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		25.50%
OGE Energy [Member]
Schedule of Equity Method Investments [Line Items]
Percentage Share of Management Rights		50.00%
CenterPoint [Member]
Schedule of Equity Method Investments [Line Items]
Percentage Share of Management Rights		50.00%
Energy Transfer
Schedule of Equity Method Investments [Line Items]
Common Stock, Terms of Conversion		0.8595
Natural Gas Midstream Operations [Member]
Schedule of Equity Method Investments [Line Items]
Equity in earnings (losses) of unconsolidated affiliates		$ (668)	[2]	$ 113.9	$ 152.8
[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.

Investment in Unconsolidated _4

Investment in Unconsolidated Affiliate Summarized Balance Sheet Information of Equity Method Investment (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Summarized Financial Information of Equity Method Investment [Line Items]
Assets, Current	$ 428.5	$ 430.2
Liabilities, Current	697.4	657.9
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Summarized Financial Information of Equity Method Investment [Line Items]
Assets, Current	381	389
Assets, Noncurrent	11,348	11,877
Liabilities, Current	582	780
Liabilities, Noncurrent	$ 4,052	$ 4,077

Investment in Unconsolidated _5

Investment in Unconsolidated Affiliate Summarized Income Statement of Equity Method Investment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Operating Income	$ 465	$ 569	$ 648
Operating revenues	2,122.3	2,231.6	2,270.3
Net income (loss)	(173.7)	433.6	425.5
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Operating revenues	2,463	2,960	3,431
Cost of Revenue	965	1,279	1,819
Net income (loss)	$ 52	$ 360	$ 485.3

Investment in Unconsolidated _6

Investment in Unconsolidated Affiliate Reconciliation of Equity in Earnings of Unconsolidated Affiliates (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		25.50%		25.50%	25.60%
Proportionate Unconsolidated Affiliate Net Income		$ 13.2		$ 91.8	$ 124.4
Amortization of basis difference and dilution recognition	[1]	98.8		22.1	28.4
Equity Method Investment, Other than Temporary Impairment		(780)		0	0
Equity in earnings of unconsolidated affiliates	[2]	(668)	[3]	113.9	152.8
Net income (loss)		(173.7)		433.6	425.5
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Net income (loss)		52		360	485.3
Natural Gas Midstream Operations [Member]
Schedule of Equity Method Investments [Line Items]
Equity in earnings of unconsolidated affiliates		(668)	[3]	113.9	152.8
Net income (loss)		$ (515)		$ 81.4	$ 108.8
OGE Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		25.50%
OGE Energy [Member]
Schedule of Equity Method Investments [Line Items]
Amortization of basis difference and dilution recognition	[4]	$ 100.2
[1]	Includes loss on dilution, net of proportional basis difference recognition.
[2]	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.
[3]	In March 2020, OGE Energy recorded a $780.0 million impairment on its investment in Enable, as further discussed in Notes 5 and 7.
[4]	Includes proportional basis difference recognition due to dilution.

Related Party Disclosures (Deta

Related Party Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Expected Settlement Charge	$ 19
Excluding Fuel Purchases [Member]
Related Party Transaction [Line Items]
Accounts receivable - unconsolidated affiliates	2	$ 0.8
Og and E [Member]
Related Party Transaction [Line Items]
Dividends, Common Stock	325		$ 185
Og and E [Member] | Retained Earnings
Related Party Transaction [Line Items]
Dividends, Common Stock	(325)	0	185
Enable Midstream Partners [Member] | Og and E [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	15.1	15.9	16.3
Enable Midstream Partners [Member] | Og and E [Member] | Natural Gas Transportation [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	32.8	41.2	37.9
Enable Midstream Partners [Member] | Og and E [Member] | Natural Gas Purchases [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	2.7	(6)	(3.2)
Enable Midstream Partners [Member] | OGE Energy [Member] | Operating Costs Charged [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	0.4	0.5	0.6
Enable Midstream Partners [Member] | OGE Energy [Member] | Employment Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	17.3	23.2	27.5
Og and E [Member] | OGE Energy [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	$ 140.6	$ 149.8	$ 140.9

Fair Value Measurements Carryin

Fair Value Measurements Carrying and Fair Value Amounts (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	$ 3,494.4	$ 3,195.2
OG&E Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	3,349.6	3,050.3
Long-Term Debt, Fair Value	4,182.1	3,500.4
OG&E Industrial Authority Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	135.4	135.4
Long-Term Debt, Fair Value	135.4	135.4
OG&E Tinker Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	9.4	9.5
Long-Term Debt, Fair Value	10.7	10
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ 0	$ 0

Stock Based Compensation (Detai

Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized				7,400,000
Tax Benefit from Compensation Expense				$ 2.5		$ 3.6	$ 3.4
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				247,252
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				247,252
Minimum payout range				0.00%
Maximum payout range				200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				247,252
Total Compensation Cost Not yet Recognized				$ 8.7
Treasury Stock, Shares, Acquired				405,000
Treasury Stock Acquired, Average Cost Per Share		$ 33.14	$ 38.04
Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax Benefit from Compensation Expense				$ 0.8		$ 1.3	$ 1.2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total Compensation Cost Not yet Recognized				$ 2.2
Performance Units Related to Earnings Per Share [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				0			87,308
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 0		$ 31.03
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number				79,002		155,171
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				0			87,308
Equity Instruments Other than Options, Converted in Period	[1]			(74,053)
Equity Instruments Other than Options, Forfeited in Period				(2,116)
Awards Other than Options, Fully Vested				79,002
Equity Instruments Other than Options, Converted, Aggregrate Intrinsic Value				$ 6.6
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value				(2.7)
Equity Instruments Other than Options, Outstanding, Aggregrate Intrinsic Value				$ 2.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				81,118
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				0			87,308
Equity Instruments Other than Options, Vested in Period				(79,002)
Equity Instruments Other than Options, Forfeited in Period				(2,116)
Equity Instruments Other than Options, Nonvested, Number, Ending Balance				0		81,118
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 0		$ 31.03
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				0		$ 31.03
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value				31.03
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 31.03
Fair Value of Vested Performance Units and Restricted Stock				$ 2.5		$ 5.2	$ 4.9
Performance Units Related to Earnings Per Share [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				0			30,649
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number				25,235		53,977
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				0			30,649
Equity Instruments Other than Options, Converted in Period	[1]			(25,931)
Equity Instruments Other than Options, Forfeited in Period				(1,969)
Equity Other Than Options, Employee Migration	[2]			(842)
Awards Other than Options, Fully Vested				25,235
Equity Other Than Options, Employee Migration, Weighted Average Grant Date Fair Value				$ 31.03
Equity Instruments Other than Options, Converted, Aggregrate Intrinsic Value				$ 2.3
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value				(0.8)
Equity Instruments Other than Options, Outstanding, Aggregrate Intrinsic Value				$ 0.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				28,046
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				0			30,649
Equity Instruments Other than Options, Vested in Period				(25,235)
Equity Instruments Other than Options, Forfeited in Period				(1,969)
Equity Other Than Options, Employee Migration	[2]			(842)
Equity Instruments Other than Options, Nonvested, Number, Ending Balance				0		28,046
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 0		$ 31.03
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				0
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value				31.03
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 31.03
Fair Value of Vested Performance Units and Restricted Stock				$ 0.8		$ 0.9	$ 1.7
Total Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				201,552	[3]	208,647	261,916
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 38.03		$ 47	$ 36.86
Expected Dividend Rate				3.50%		4.00%	3.60%
Expected Volatility Rate				15.00%		17.00%	19.00%
Risk Free Interest Rate				1.17%		2.47%	2.38%
Expected Term				2 years 10 months 6 days		2 years 10 months 9 days	2 years 10 months 9 days
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number				612,262		664,817
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				201,552	[3]	208,647	261,916
Equity Instruments Other than Options, Converted in Period	[1]			(222,163)
Equity Instruments Other than Options, Forfeited in Period				(31,944)
Awards Other than Options, Fully Vested				236,990
Equity Instruments Other than Options, Converted, Aggregrate Intrinsic Value				$ 11.5
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value				(5.4)
Equity Instruments Other than Options, Outstanding, Aggregrate Intrinsic Value				$ 5.4
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				442,654
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				201,552	[3]	208,647	261,916
Equity Instruments Other than Options, Vested in Period				(236,990)
Equity Instruments Other than Options, Forfeited in Period				(31,944)
Equity Instruments Other than Options, Nonvested, Number, Ending Balance				375,272		442,654
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 42.51		$ 41.43
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				38.03		$ 47	$ 36.86
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value				36.86
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 41.15
Fair Value of Vested Performance Units and Restricted Stock				$ 8.7		$ 9.3	$ 5.9
Total Compensation Cost Not yet Recognized				$ 7.1
Total Compensation Cost Not yet Recognized, Period for Recognition				1 year 7 months 13 days
Total Shareholder Return [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				67,975	[4]	68,396	91,940
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 38.03		$ 47	$ 36.86
Expected Dividend Rate				3.50%		4.00%	3.60%
Expected Volatility Rate				15.00%		17.00%	19.00%
Risk Free Interest Rate				1.17%		2.47%	2.38%
Expected Term				2 years 10 months 6 days		2 years 10 months 9 days	2 years 10 months 9 days
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number				182,363		227,679
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				67,975	[4]	68,396	91,940
Equity Instruments Other than Options, Converted in Period	[1]			(77,799)
Equity Instruments Other than Options, Forfeited in Period				(28,985)
Equity Other Than Options, Employee Migration	[5]			(6,507)
Awards Other than Options, Fully Vested				75,693
Equity Other Than Options, Employee Migration, Weighted Average Grant Date Fair Value				$ 40.26
Equity Instruments Other than Options, Converted, Aggregrate Intrinsic Value				$ 4
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value				(1.7)
Equity Instruments Other than Options, Outstanding, Aggregrate Intrinsic Value				$ 1.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				149,880
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				67,975	[4]	68,396	91,940
Equity Instruments Other than Options, Vested in Period				(75,693)
Equity Instruments Other than Options, Forfeited in Period				(28,985)
Equity Other Than Options, Employee Migration	[5]			(6,507)
Equity Instruments Other than Options, Nonvested, Number, Ending Balance				106,670		149,880
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 42.49		$ 41.31
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				38.03		$ 47	$ 36.86
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value				36.86
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 41.12
Fair Value of Vested Performance Units and Restricted Stock				$ 2.8		$ 3.2	$ 2.1
Total Compensation Cost Not yet Recognized				$ 1.8
Total Compensation Cost Not yet Recognized, Period for Recognition				1 year 7 months 20 days
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				$ 8.9		13	13.3
Performance Shares [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				2.6		4.5	4.6
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				$ 0.9		$ 0.9	$ 0.1
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				67,193		75,929	826
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 43.69		$ 41.71	$ 36.28
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number				124,919		72,880
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				67,193		75,929	826
Equity Instruments Other than Options, Forfeited in Period				(12,546)
Awards Other than Options, Fully Vested				1,752
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value				$ (0.1)
Equity Instruments Other than Options, Outstanding, Aggregrate Intrinsic Value				$ 4
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				72,880
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				67,193		75,929	826
Equity Instruments Other than Options, Vested in Period				(2,608)
Equity Instruments Other than Options, Forfeited in Period				(12,546)
Equity Instruments Other than Options, Nonvested, Number, Ending Balance				124,919		72,880
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 42.69		$ 41.66
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				43.69		$ 41.71	$ 36.28
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value				40.30
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 42.60
Fair Value of Vested Performance Units and Restricted Stock				$ 0.1		$ 0.1	$ 0.1
Total Compensation Cost Not yet Recognized				$ 1.6
Total Compensation Cost Not yet Recognized, Period for Recognition				1 year 7 months 24 days
Restricted Stock [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				$ 0.4		$ 0.4	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				22,665		26,141	0
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 43.69		$ 41.63	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number				34,130		25,005
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				22,665		26,141	0
Equity Instruments Other than Options, Forfeited in Period				(11,100)
Equity Other Than Options, Employee Migration	[2]			(1,327)
Awards Other than Options, Fully Vested				1,114
Equity Other Than Options, Employee Migration, Weighted Average Grant Date Fair Value				$ 42.76
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value				$ 0
Equity Instruments Other than Options, Outstanding, Aggregrate Intrinsic Value				$ 1.1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				25,005
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted				22,665		26,141	0
Equity Instruments Other than Options, Vested in Period				(1,113)
Equity Instruments Other than Options, Forfeited in Period				(11,100)
Equity Other Than Options, Employee Migration	[2]			(1,327)
Equity Instruments Other than Options, Nonvested, Number, Ending Balance				34,130		25,005
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value				$ 42.67		$ 41.62
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				43.69		$ 41.63	$ 0
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value				40.59
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 42.60
Fair Value of Vested Performance Units and Restricted Stock				$ 0.1		$ 0	$ 0
Total Compensation Cost Not yet Recognized				$ 0.4
Total Compensation Cost Not yet Recognized, Period for Recognition				1 year 8 months 4 days
Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				$ 9.8		13.9	13.4
Stock Compensation Plan [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				3		4.9	4.6
Performance Units Related to Earnings Per Share [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				1		4.3	5.1
Performance Units Related to Earnings Per Share [Member] | Performance Shares [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				0.3		1.5	1.8
Total Shareholder Return [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				7.9		8.7	8.2
Total Shareholder Return [Member] | Performance Shares [Member] | Og and E [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense				$ 2.3		$ 3	$ 2.8
[1]	These amounts represent performance units that vested at December 31, 2019 which were settled in March 2020.
[2]	Due to certain employees transferring between OG&E and OGE Energy.
[3]	For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target.
[4]	For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target.
[5]	Due to certain employees transferring between OG&E and OGE Energy.

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulatory Liability, Noncurrent		$ 1,188.9	$ 1,223.5
Current Federal Tax Expense (Benefit)		8.4	(6.4)	$ (1.9)
Current State and Local Tax Expense (Benefit)		0.5	5.1	(4.4)
Current Income Tax Expense (Benefit)		8.9	(1.3)	(6.3)
Deferred Federal Income Tax Expense (Benefit)		(105.2)	48.5	74.7
Deferred State and Local Income Tax Expense (Benefit)		(31.1)	(17.4)	3.7
Deferred Income Tax Expense (Benefit)		(136.3)	31.1	78.4
Investment Tax Credit		0	0	0.1
Income Tax Expense (Benefit)		$ (127.4)	$ 29.8	$ 72.2
Statutory federal tax rate		21.00%	21.00%	21.00%
Federal deferred tax revaluation		0.00%	0.00%	0.40%
Federal renewable energy credit (B)	[1]	(5.00%)	(6.00%)	(5.10%)
Remeasurement of state deferred tax liabilities		0.90%	(0.80%)	(0.40%)
401(k) dividends		(0.40%)	(0.40%)	(0.30%)
State income taxes, net of federal income tax benefit		(1.40%)	(1.20%)	0.40%
Effective Income Tax Rate Reconciliation, Executive Compensation Limitation, Percent		0.20%	0.20%	0.20%
Amortization of net unfunded deferred taxes		(4.40%)	(4.50%)	(2.10%)
Other		0.10%	(0.70%)	0.40%
Effective income tax rate		42.30%	6.40%	14.50%
Accrued liabilities		$ (9.6)	$ (10.7)
Accrued vacation		(2.2)	(2.1)
Uncollectible accounts		(0.7)	(0.4)
Accelerated depreciation and other property related differences		1,721.2	1,656.8
Investment in Enable		302.6	478.2
Regulatory assets		52.3	28.4
Income taxes recoverable from customers, net		(221.8)	(229.9)
Pension Plan		3.9	4.1
Bond redemption-unamortized costs		2	2.2
Derivative instruments		1.7	1.6
Federal tax credits		(236.6)	(238)
State tax credits		(204.4)	(185.8)
Postretirement medical and life insurance benefits		(22.4)	(23.3)
Net operating losses		(12)	(16.6)
Regulatory liabilities		(81)	(68.1)
Asset retirement obligations		(20.3)	(19.2)
Deferred federal investment tax credits		(2.7)	(1.8)
Other		(1.4)	0.4
Total deferred income tax liabilities, net		1,268.6	1,375.8
Unrecognized Tax Benefits		21.9	20.7	$ 20.7	$ 20.7
Current year additions		1.2	0	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		0
Tax Credit Carryforward, Deferred Tax Asset		$ 236.6	$ 238
Stock-based compensation		(0.30%)	(1.20%)	0.00%
Effective Income Tax Rate Reconciliation, Tax Contingency, Percent	[2]	31.60%	0.00%	0.00%
Deferred Tax Asset [Member]
Unrecognized Tax Benefits		$ 17.6
State operating loss [Member]
Operating Loss Carryforwards		268
Deferred Tax Assets, Operating Loss Carryforwards, State and Local		12
Federal tax credits [Member]
Federal tax credits		(236.6)
Tax Credit Carryforward, Amount		236.6
Tax Credit Carryforward, Deferred Tax Asset		236.6
Oklahoma investment tax credits [Member]
State tax credits		(162.3)
Tax Credit Carryforward, Amount		205.6
Oklahoma capital investment board credits [Member]
State tax credits		(12.7)
Tax Credit Carryforward, Amount		12.7
Oklahoma zero emission tax credits [Member]
State tax credits		(29.3)
Tax Credit Carryforward, Amount		37.2
Louisiana inventory credits
State tax credits		(0.1)
Tax Credit Carryforward, Amount		0.2
Research and Development Credits [Member]
Tax Credit Carryforward, Amount		1.2
Og and E [Member]
Regulatory Liability, Noncurrent		1,188.9	$ 1,223.5
Current Federal Tax Expense (Benefit)		(3.8)	(7.9)	$ (12.4)
Current State and Local Tax Expense (Benefit)		(0.6)	4.1	(4.1)
Current Income Tax Expense (Benefit)		(4.4)	(3.8)	(16.5)
Deferred Federal Income Tax Expense (Benefit)		45.7	37.7	53.7
Deferred State and Local Income Tax Expense (Benefit)		(6.6)	(13.8)	2.7
Deferred Income Tax Expense (Benefit)		39.1	23.9	56.4
Investment Tax Credit		0	0	0.1
Income Tax Expense (Benefit)		$ 34.7	$ 20.1	$ 40
Statutory federal tax rate		21.00%	21.00%	21.00%
Federal deferred tax revaluation		0.00%	0.00%	0.00%
Federal renewable energy credit (B)	[1]	(5.40%)	(7.60%)	(6.90%)
Remeasurement of state deferred tax liabilities		0.00%	0.00%	0.00%
401(k) dividends		0.00%	0.00%	0.00%
State income taxes, net of federal income tax benefit		(1.60%)	(1.80%)	(0.20%)
Effective Income Tax Rate Reconciliation, Executive Compensation Limitation, Percent		0.00%	0.00%	0.00%
Amortization of net unfunded deferred taxes		(4.80%)	(5.60%)	(2.90%)
Other		0.10%	(0.60%)	(0.10%)
Effective income tax rate		9.30%	5.40%	10.90%
Accrued liabilities		$ (5.2)	$ (4.3)
Accrued vacation		(1.6)	(1.6)
Uncollectible accounts		(0.7)	(0.4)
Accelerated depreciation and other property related differences		1,721.2	1,656.8
Investment in Enable		0	0
Regulatory assets		52.3	28.4
Income taxes recoverable from customers, net		(221.8)	(229.9)
Pension Plan		27.4	24.5
Bond redemption-unamortized costs		2	2.2
Derivative instruments		0	0
Federal tax credits		(236.6)	(238)
State tax credits		(189)	(170.8)
Postretirement medical and life insurance benefits		(15.3)	(16)
Net operating losses		(1.4)	(5.7)
Regulatory liabilities		(81)	(68.1)
Asset retirement obligations		(20.3)	(19.2)
Deferred federal investment tax credits		(2.7)	(1.8)
Other		(6.5)	(4.7)
Total deferred income tax liabilities, net		1,020.8	951.4
Unrecognized Tax Benefits		17.6	16.4	$ 16.4
Tax Credit Carryforward, Deferred Tax Asset		$ 236.6	$ 238
Stock-based compensation		0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Contingency, Percent	[2]	0.00%	0.00%	0.00%
Og and E [Member] | State operating loss [Member]
Operating Loss Carryforwards		$ 21.5
Deferred Tax Assets, Operating Loss Carryforwards, State and Local		1.4
Og and E [Member] | Federal tax credits [Member]
Federal tax credits		(236.6)
Tax Credit Carryforward, Amount		236.6
Tax Credit Carryforward, Deferred Tax Asset		236.6
Og and E [Member] | Oklahoma investment tax credits [Member]
State tax credits		(147)
Tax Credit Carryforward, Amount		186.1
Og and E [Member] | Oklahoma capital investment board credits [Member]
State tax credits		(12.7)
Tax Credit Carryforward, Amount		12.7
Og and E [Member] | Oklahoma zero emission tax credits [Member]
State tax credits		(29.3)
Tax Credit Carryforward, Amount		37.2
Og and E [Member] | Louisiana inventory credits
State tax credits		0
Tax Credit Carryforward, Amount		$ 0
[1]	Represents credits primarily associated with the production from OG&E's wind farms.
[2]	As further discussed in Note 5, OGE Energy recorded a $780.0 million impairment on its investment in Enable in March 2020, which resulted in a tax benefit being recorded that caused a significant variance to the effective tax rate as compared to the prior year. This variance has been presented in the table as a single line item in order to facilitate comparability of other components of the effective tax rate.

Common Equity Automatic Dividen

Common Equity Automatic Dividend Reinvestment and Stock Purchase Plan (Details) - Automatic Dividend Reinvestment and Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2020shares
Stock Issued During Period, Shares, Dividend Reinvestment Plan and Stock Purchase Plan	0
Shares Held in Reserve Related to Dividend Reinvestment Plan and Stock Purchase Plan	4,774,442

Common Equity Earnings Per Shar

Common Equity Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	300	0	0
Net income attributable to OGE Energy	$ (173.7)	$ 433.6	$ 425.5
Basic Average Common Shares Outstanding	200,100	200,100	199,700
Contingently Issuable Shares (Performance and Restricted Stock Units)	0	600	800
Diluted Average Common Shares Outstanding	200,100	200,700	200,500
Earnings Per Share, Basic and Diluted [Abstract]
Basic earnings per average common share attributable to OGE Energy common shareholders	$ (0.87)	$ 2.17	$ 2.13
Diluted earnings per average common share attributable to OGE Energy common shareholders	$ (0.87)	$ 2.16	$ 2.12
Og and E [Member]
Stock Issued During Period, Shares, New Issues	0	0	0
Retained Earnings [Member]
Net income attributable to OGE Energy	$ (173.7)	$ 433.6	$ 425.5

Common Equity Dividends Restric

Common Equity Dividends Restriction (Details) shares in Millions, $ in Millions	Dec. 31, 2020USD ($)shares
Preferred Stock, Shares Outstanding | shares	0
OGE Energy [Member]
Ratio of Consolidated Debt to Consolidated Capitalization	65.00%
Retained Earnings, Restricted	$ 815
Retained Earnings, Unrestricted	$ 1,700
Og and E [Member]
Ratio of Consolidated Debt to Consolidated Capitalization	65.00%
Retained Earnings, Restricted	$ 842.7
Retained Earnings, Unrestricted	$ 2,100

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total long-term debt	$ 3,494.4	$ 3,195.2
Percent of Principal Amount Subject to Optional Tender	100.00%
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 0
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	$ 0
Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Date Due	Jan. 1, 2025
Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Date Due	Jan. 1, 2025
Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Date Due	Jun. 1, 2027
Redeemable during the next 12 months
Debt Instrument [Line Items]
Total long-term debt	$ 135.4
OG&E [Member]
Debt Instrument [Line Items]
Total long-term debt	3,494.4	3,195.2
OG&E [Member] | Redeemable during the next 12 months | Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Long term debt, gross	47	47
OG&E [Member] | Redeemable during the next 12 months | Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Long term debt, gross	32.4	32.4
OG&E [Member] | Redeemable during the next 12 months | Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Long term debt, gross	56	56
Senior Notes [Member] | OG&E [Member] | Series Due April 1, 2030
Debt Instrument [Line Items]
Long term debt, gross	$ 300	$ 0
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Date Due	Apr. 1, 2030
Debt Instrument, Face Amount	$ 300
Minimum [Member] | Redeemable during the next 12 months | Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.28%
Minimum [Member] | Redeemable during the next 12 months | Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.33%
Minimum [Member] | Redeemable during the next 12 months | Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.28%
Maximum [Member] | Redeemable during the next 12 months | Garfield Industrial Authority, January 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.35%
Maximum [Member] | Redeemable during the next 12 months | Muskogee Industrial Authority, Janaury 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.31%
Maximum [Member] | Redeemable during the next 12 months | Muskogee Industrial Authority, June 1, 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.35%

Short-Term Debt and Credit Fa_3

Short-Term Debt and Credit Facilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Short-term debt		$ 95	$ 112
Line of Credit Facility [Abstract]
Aggregate Commitment		900
Amount Outstanding	[1]	$ 95.4
Weighted Average Interest Rate		0.25%
Proceeds from Unsecured Lines of Credit		$ 75
Repayments of Unsecured Debt		75
Other Commitment		1,000
Acceleration of Indebtedness of Credit Facility		100
Nonpayment of Uninsured Judgments		100
OGE Energy [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	[2]	450
Line of Credit Facility [Abstract]
Amount Outstanding	[1],[2]	$ 95
Weighted Average Interest Rate	[2],[3]	0.25%
Maturity	[2],[4]	Mar. 8, 2024
Ratio of Consolidated Debt to Consolidated Capitalization		65.00%
OGE Energy [Member] | Not Extended
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity		$ 50
Line of Credit Facility [Abstract]
Maturity		Mar. 8, 2023
OG&E [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	[5],[6]	$ 450
Line of Credit Facility [Abstract]
Letters of Credit Outstanding, Amount	[1],[5],[6]	$ 0.4
Weighted Average Interest Rate	[3],[5],[6]	1.00%
Maturity	[4],[5],[6]	Mar. 8, 2024
Intercompany Borrowing Agreement - Maximum Borrowing Capacity		$ 350
Period For Which Regulatory Approval Has Been Given to Acquire Short Term Debt		2 years
Short Term Borrowing Capacity That Has Regulatory Approval		$ 800
Ratio of Consolidated Debt to Consolidated Capitalization		65.00%
Outstanding Intercompany Borrowings		$ 0
[1]	Includes direct borrowings under the revolving credit agreements, commercial paper borrowings and letters of credit at December 31, 2020.
[2]	This bank facility is available to back up OGE Energy's commercial paper borrowings and to provide revolving credit borrowings. This bank facility can also be used as a letter of credit facility.
[3]	Represents the weighted-average interest rate for the outstanding borrowings under the revolving credit agreements, commercial paper borrowings and letters of credit.
[4]	In March 2017, the Registrants entered into unsecured five-year revolving credit agreements totaling $900.0 million ($450.0 million for OGE Energy and $450.0 million for OG&E). Each of the revolving credit facilities contained an option, which could be exercised up to two times, to extend the term of the respective facility for an additional year. In March 2018, the Registrants each utilized one of those extensions to extend the maturity of their respective credit facility from March 8, 2022 to March 8, 2023. In January 2021, the Registrants each utilized the second of those extensions to extend the maturity of their respective credit facility from March 8, 2023 to March 8, 2024. Commitments of a single existing lender with respect to $50.0 million of OGE Energy's credit facility, however, were not extended and, unless the non-extending lender is replaced in accordance with the terms of the credit facility, such commitments will expire March 8, 2023. The non-extending lender is not party to the OG&E facility.
[5]	OG&E has an intercompany borrowing agreement with OGE Energy whereby OG&E has access to up to $350.0 million of OGE Energy's revolving credit amount. This agreement has a termination date of March 8, 2024. At December 31, 2020, there were no intercompany borrowings under this agreement.
[6]	This bank facility is available to back up OG&E's commercial paper borrowings and to provide revolving credit borrowings. This bank facility can also be used as a letter of credit facility.

Retirement Plans and Postreti_3

Retirement Plans and Postretirement Benefit Plans (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2021	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match			200.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay			5.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions		$ 40	$ 20		$ 20
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Ultimate Health Care Cost Trend Rate			4.50%
Expected Future Benefit Payments, Next Twelve Months			$ 164.2
Expected Future Benefit Payments, Year Two			43.3
Expected Future Benefit Payments, Year Three			42.5
Expected Future Benefit Payments, Year Four			44.2
Expected Future Benefit Payments, Year Five			41.1
Expected Future Benefit Payments, Five Fiscal Years Thereafter			203.6
Defined Contribution Plan, Cost			18.2		14.4		$ 13.2
Postemployment Benefits Liability			2.2		2.1
Og and E [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions			10		5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Expected Future Benefit Payments, Next Twelve Months			123.9
Expected Future Benefit Payments, Year Two			33.1
Expected Future Benefit Payments, Year Three			31.9
Expected Future Benefit Payments, Year Four			32.3
Expected Future Benefit Payments, Year Five			29.3
Expected Future Benefit Payments, Five Fiscal Years Thereafter			141.1
Defined Contribution Plan, Cost			14.3		11		9.8
Postemployment Benefits Liability			1.8		1.7
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid			(14.2)		(14.6)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0		0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		654.6	616.1		615.9
Service cost			13.2		12.9		14.9
Interest cost			17		20.7		23.8
Plan curtailments			0		0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits			7.6		0
Plan settlements			(42.8)		(83.1)
Actuarial losses			57.7		64.3
Benefit Obligation, Ending			654.6		616.1		615.9
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		570.3	530.3		522.8
Actual return on plans' assets			77		85.2
Employer contributions			20		20
Plan settlements			(42.8)		(83.1)
Fair Value of Plan Assets, Ending			570.3		530.3		522.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			13.2		12.9		14.9
Interest cost			17		20.7		23.8
Expected return on plan assets			(37.6)		(36.1)		(44.1)
Defined Benefit Plan, Amortization of Gain (Loss)			(17.1)		(17.3)		(16.2)
Amortization of unrecognized prior service cost	[1]		0		0		0
Curtailment			0		0		0
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits			7.6		0		0
Settlement cost			14.1		27.6		25.1
Net periodic benefit cost			31.4		42.4		35.9
Amount paid by unconsolidated affiliates	[2]		2		2.9		2.5
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			29.4		39.5		33.4
Plan settlements			(42.8)		(83.1)
Capitalized Portion of Net Periodic Benefit Cost			$ 3.8		$ 3.6		$ 3.8
Assumptions Used Calculating Benefit Obligation, Discount Rate			2.30%		3.15%		4.20%
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets			7.50%		7.50%		7.50%
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase			4.20%		4.20%		4.20%
Fair Value of Plan Assets, Beginning		570.3	$ 530.3		$ 522.8
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(14.2)		(14.6)
Accumulated Benefit Obligation			(610.8)		(563.3)
Pension Plans, Defined Benefit [Member] | Og and E [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid			(12.3)		(12.7)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		484.1	462		453.6
Service cost			9.2		9		$ 9.8
Interest cost			12.6		15.6		17.6
Plan curtailments			0		0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits			5.1		0
Plan settlements			(33.5)		(45.6)
Actuarial losses			41		42.1
Benefit Obligation, Ending			484.1		462		453.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		420.3	399.1		387.6
Actual return on plans' assets			57		64.8
Employer contributions			10		5
Plan settlements			(33.5)		(45.6)
Fair Value of Plan Assets, Ending			420.3		399.1		387.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			9.2		9		9.8
Interest cost			12.6		15.6		17.6
Expected return on plan assets			(27.9)		(27.6)		(33.1)
Defined Benefit Plan, Amortization of Gain (Loss)			(12.1)		(12.9)		(12.1)
Amortization of unrecognized prior service cost			0		0		0
Curtailment			0		0		0
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits			5.1		0		0
Settlement cost			11.4		16.4		19.4
Net periodic benefit cost			22.5		26.3		25.8
Amount Attributable to Parent	[2]		5.9		4.5		5.7
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			28.4		30.8		31.5
Plan settlements			(33.5)		(45.6)
Capitalized Portion of Net Periodic Benefit Cost			3.1		3		3.2
Fair Value of Plan Assets, Beginning		420.3	399.1		387.6
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(12.3)		(12.7)
Accumulated Benefit Obligation			(454.7)		(425.8)
Pension Plans, Defined Benefit [Member] | OKLAHOMA
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement cost	[3]		21.6		17.9		22.1
Additional Pension Expense to Meet State Requirements			(13.8)	[3]	(16.1)		(14.1)
Pension Plans, Defined Benefit [Member] | ARKANSAS
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement cost	[3]		2		1.7		2.1
Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Restoration of Retirement Income Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid			0		0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0		0.3
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		7.8	10.3		9.6
Service cost			0.8		0.5		0.4
Interest cost			0.2		0.4		0.3
Plan curtailments			0.2		0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits			0		0
Plan settlements			(5.3)		(1.2)
Actuarial losses			1.6		0.7
Benefit Obligation, Ending			7.8		10.3		9.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0		0
Actual return on plans' assets			0		0
Employer contributions			5.3		1.2
Plan settlements			(5.3)		(1.2)
Fair Value of Plan Assets, Ending			0		0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.8		0.5		0.4
Interest cost			0.2		0.4		0.3
Expected return on plan assets			0		0		0
Defined Benefit Plan, Amortization of Gain (Loss)			(0.5)		(0.5)		(0.7)
Amortization of unrecognized prior service cost	[1]		0		0		0.1
Curtailment			0.2		0		0
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits			0		0		0
Settlement cost			2.7		0.5		1
Net periodic benefit cost			4.4		1.9		2.5
Amount paid by unconsolidated affiliates	[2]		0.1		0.1		0.1
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			4.3		1.8		2.4
Plan settlements			(5.3)		(1.2)
Fair Value of Plan Assets, Beginning		0	0		0
Defined Benefit Plan, Benefit Obligation, Benefits Paid			0		0
Accumulated Benefit Obligation			(6.9)		(8.1)
Restoration of Retirement Income Plan [Member] | Og and E [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid			0		0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		3	6.1		6
Service cost			0.1		0.2		0.2
Interest cost			0.1		0.2		0.2
Plan curtailments			0		0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits			0		0
Plan settlements			(4.5)		(0.9)
Actuarial losses			1.2		0.6
Benefit Obligation, Ending			3		6.1		6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0		0
Actual return on plans' assets			0		0
Employer contributions			4.5		0.9
Plan settlements			(4.5)		(0.9)
Fair Value of Plan Assets, Ending			0		0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.1		0.2		0.2
Interest cost			0.1		0.2		0.2
Expected return on plan assets			0		0		0
Defined Benefit Plan, Amortization of Gain (Loss)			(0.4)		(0.3)		(0.5)
Amortization of unrecognized prior service cost			0		0		0
Curtailment			0		0		0
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits			0		0		0
Settlement cost			2.4		0.5		0.4
Net periodic benefit cost			3		1.2		1.3
Amount Attributable to Parent	[2]		1.3		0.5		1.2
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			4.3		1.7		2.5
Plan settlements			(4.5)		(0.9)
Fair Value of Plan Assets, Beginning		0	0		0
Defined Benefit Plan, Benefit Obligation, Benefits Paid			0		0
Accumulated Benefit Obligation			(2.9)		(4.8)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid			(11)		(12.1)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0		0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		144.5	136.5		135.8
Service cost			0.2		0.2		0.3
Interest cost			4.2		5.6		5.4
Plan curtailments			4		0
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant			(3.3)		(4.1)
Actuarial losses			7.3		2.9
Benefit Obligation, Ending			144.5		136.5		135.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		47.6	47		45.3
Actual return on plans' assets			1.2		4.6
Employer contributions			7.1		5.1
Fair Value of Plan Assets, Ending			47.6		47		45.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.2		0.2		0.3
Interest cost			4.2		5.6		5.4
Expected return on plan assets			(1.8)		(1.9)		(2)
Defined Benefit Plan, Amortization of Gain (Loss)			(2)		(2)		(3.8)
Amortization of unrecognized prior service cost	[1]		(8.4)		(8.4)		(8.4)
Curtailment			(1.5)		0		0
Net periodic benefit cost			(2.3)		(2.5)		(0.9)
Amount paid by unconsolidated affiliates	[4]		(0.7)		(0.6)		(0.5)
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			(1.6)		(1.9)		(0.4)
Capitalized Portion of Net Periodic Benefit Cost			$ 0.2		$ 0.2		$ 0.2
Assumptions Used Calculating Benefit Obligation, Discount Rate			2.45%		3.25%		4.30%
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets			4.00%		4.00%		4.00%
Health Care Cost Trend Rate Assumed for Next Fiscal Year			6.75%
Fair Value of Plan Assets, Beginning		47.6	$ 47		$ 45.3
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant			3.3		4.1
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(11)		(12.1)
Accumulated Benefit Obligation			(96.9)		(89.5)
Other Postretirement Benefits Plan [Member] | Og and E [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid			(8.6)		(9.8)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		109.5	104.7		104.8
Service cost			0.2		0.2		$ 0.2
Interest cost			3.2		4.3		4.2
Plan curtailments			3.1		0
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant			(2.4)		(3)
Actuarial losses			4.5		2.2
Benefit Obligation, Ending			109.5		104.7		104.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		42.7	41.9		40.6
Actual return on plans' assets			1.1		4
Employer contributions			5.9		4.1
Fair Value of Plan Assets, Ending			42.7		41.9		40.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.2		0.2		0.2
Interest cost			3.2		4.3		4.2
Expected return on plan assets			(1.7)		(1.7)		(1.8)
Defined Benefit Plan, Amortization of Gain (Loss)			(2.1)		(2.1)		(3.8)
Amortization of unrecognized prior service cost	[1]		(6.1)		(6.1)		(6.1)
Curtailment			(1.3)		0		0
Net periodic benefit cost			(1)		(1.2)		0.3
Amount Attributable to Parent	[4]		(0.5)		(0.6)		(0.7)
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			(1.5)		(1.8)		(0.4)
Capitalized Portion of Net Periodic Benefit Cost			0.1		0.1		0.1
Fair Value of Plan Assets, Beginning		42.7	41.9		40.6
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant			2.4		3
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(8.6)		(9.8)
Accumulated Benefit Obligation			(66.8)		(62.8)
Other Postretirement Benefits Plan [Member] | OKLAHOMA
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement cost			1.4		0		0
Additional Pension Expense to Meet State Requirements	[5]		0.2		1		4.4
Other Postretirement Benefits Plan [Member] | ARKANSAS
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement cost			0.1		0		$ 0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		14.2	12.1
Fair Value of Plan Assets, Ending			14.2		12.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		14.2	12.1
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		33.4	34.8
Fair Value of Plan Assets, Ending			33.4		34.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		33.4	34.8
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		47.6	46.9
Fair Value of Plan Assets, Ending			47.6		46.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		47.6	46.9
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member] | Og and E [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		42.7	41.9
Fair Value of Plan Assets, Ending			42.7		41.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		42.7	$ 41.9
Less Than 90% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			50.00%
Projected Benefit Obligation Funded Status Thresholds Equity			50.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
95% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			58.00%
Projected Benefit Obligation Funded Status Thresholds Equity			42.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
100% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			65.00%
Projected Benefit Obligation Funded Status Thresholds Equity			35.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
105% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			73.00%
Projected Benefit Obligation Funded Status Thresholds Equity			27.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
110% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			80.00%
Projected Benefit Obligation Funded Status Thresholds Equity			20.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
115% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			85.00%
Projected Benefit Obligation Funded Status Thresholds Equity			15.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
120% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income			90.00%
Projected Benefit Obligation Funded Status Thresholds Equity			10.00%
Projected Benefit Obligation Funded Status Thresholds			100.00%
Domestic All-Cap/Large Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			40.00%
Domestic Mid-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			15.00%
Domestic Small-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			25.00%
International Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			20.00%
Minimum [Member] | Domestic All-Cap/Large Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			35.00%
Minimum [Member] | Domestic Mid-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			5.00%
Minimum [Member] | Domestic Small-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			5.00%
Minimum [Member] | International Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			10.00%
Maximum [Member] | Domestic All-Cap/Large Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			60.00%
Maximum [Member] | Domestic Mid-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			25.00%
Maximum [Member] | Domestic Small-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			30.00%
Maximum [Member] | International Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations			30.00%
Group Retiree Medical Insurance Contract [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		33.4	$ 34.8
Fair Value of Plan Assets, Ending			33.4		34.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		33.4	34.8
Group Retiree Medical Insurance Contract [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Group Retiree Medical Insurance Contract [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		33.4	34.8
Fair Value of Plan Assets, Ending			33.4		34.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		33.4	34.8
U.S. common stocks [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		252.3	202
Fair Value of Plan Assets, Ending			252.3		202
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		252.3	202
U.S. common stocks [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		252.3	202
Fair Value of Plan Assets, Ending			252.3		202
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		252.3	202
U.S. common stocks [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
U.S. treasury notes and bonds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6],[8]	0	[7],[9]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[9]	134.3	134.8
Fair Value of Plan Assets, Ending	[9]		134.3		134.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning	[9]	134.3	134.8
U.S. treasury notes and bonds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[9]	134.3	134.8
Fair Value of Plan Assets, Ending	[9]		134.3		134.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning	[9]	134.3	134.8
U.S. treasury notes and bonds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[9]	0	0
Fair Value of Plan Assets, Ending	[9]		0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning	[9]	0	0
Mortgage-backed securities | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		29.3	45.8
Fair Value of Plan Assets, Ending			29.3		45.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		29.3	45.8
Mortgage-backed securities | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Mortgage-backed securities | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		29.3	45.8
Fair Value of Plan Assets, Ending			29.3		45.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		29.3	45.8
Corporate fixed income and other securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		116.6	130.5
Fair Value of Plan Assets, Ending			116.6		130.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		116.6	130.5
Corporate fixed income and other securities [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Corporate fixed income and other securities [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		116.6	130.5
Fair Value of Plan Assets, Ending			116.6		130.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		116.6	130.5
Commingled fund [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			25.4	[6],[10]	23.9	[7],[11]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[11]	25.4	23.9
Fair Value of Plan Assets, Ending	[11]		25.4		23.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning	[11]	25.4	23.9
Commingled fund [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[11]	0	0
Fair Value of Plan Assets, Ending	[11]		0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning	[11]	0	0
Commingled fund [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[11]	0	0
Fair Value of Plan Assets, Ending	[11]		0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning	[11]	0	0
Foreign government bonds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		4.6	3
Fair Value of Plan Assets, Ending			4.6		3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		4.6	3
Foreign government bonds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Foreign government bonds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		4.6	3
Fair Value of Plan Assets, Ending			4.6		3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		4.6	3
Municipal bonds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		1.8	1.1
Fair Value of Plan Assets, Ending			1.8		1.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		1.8	1.1
Municipal bonds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Municipal bonds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		1.8	1.1
Fair Value of Plan Assets, Ending			1.8		1.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		1.8	1.1
Money market funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			8.8	[6]	2.4	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		8.8	2.4
Fair Value of Plan Assets, Ending			8.8		2.4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		8.8	2.4
Money market funds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Money market funds [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Mutual fund [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		9.2	7.5
Fair Value of Plan Assets, Ending			9.2		7.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		9.2	7.5
Mutual fund [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		9.2	7.5
Fair Value of Plan Assets, Ending			9.2		7.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		9.2	7.5
Mutual fund [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Treasury futures, receivable [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment	[7]				0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			22.9
Fair Value of Plan Assets, Ending					22.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning			22.9
Treasury futures, receivable [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			0
Fair Value of Plan Assets, Ending					0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning			0
Treasury futures, receivable [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			22.9
Fair Value of Plan Assets, Ending					22.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning			22.9
Treasury futures, payable [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment	[7]				0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			(10.9)
Fair Value of Plan Assets, Ending					(10.9)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning			(10.9)
Treasury futures, payable [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			0
Fair Value of Plan Assets, Ending					0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning			0
Treasury futures, payable [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			(10.9)
Fair Value of Plan Assets, Ending					(10.9)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning			(10.9)
Cash collateral [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.7	0.6
Fair Value of Plan Assets, Ending			0.7		0.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.7	0.6
Cash collateral [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.7	0.6
Fair Value of Plan Assets, Ending			0.7		0.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.7	0.6
Cash collateral [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Receivable (foreign currency) [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.1	0.1
Fair Value of Plan Assets, Ending			0.1		0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.1	0.1
Receivable (foreign currency) [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Receivable (foreign currency) [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.1	0.1
Fair Value of Plan Assets, Ending			0.1		0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.1	0.1
Preferred stocks (foreign) [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			0	[6]	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.6	0.7
Fair Value of Plan Assets, Ending			0.6		0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.6	0.7
Preferred stocks (foreign) [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.6	0.7
Fair Value of Plan Assets, Ending			0.6		0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.6	0.7
Preferred stocks (foreign) [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0	0
Total Plan investments [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment			34.2	[6]	26.3	[7]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		583.7	564.4
Fair Value of Plan Assets, Ending			583.7		564.4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		583.7	564.4
Total Plan investments [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		397.1	345.6
Fair Value of Plan Assets, Ending			397.1		345.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		397.1	345.6
Total Plan investments [Member] | Pension Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		152.4	192.5
Fair Value of Plan Assets, Ending			152.4		192.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		152.4	192.5
Receivable from broker for securities sold [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.2
Fair Value of Plan Assets, Ending			0.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		0.2
Interest and dividends receivable [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		2.2	2.4
Fair Value of Plan Assets, Ending			2.2		2.4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		2.2	2.4
Payable to broker for securities purchased [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(15.8)	(36.5)
Fair Value of Plan Assets, Ending			(15.8)		(36.5)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		(15.8)	(36.5)
Total Plan assets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		570.3	530.3
Fair Value of Plan Assets, Ending			570.3		530.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		570.3	530.3
Total Plan assets [Member] | Pension Plans, Defined Benefit [Member] | Og and E [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		420.3	399.1
Fair Value of Plan Assets, Ending			420.3		399.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		420.3	399.1
Plan Assets Attributable to Affiliates | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(150)	(131.2)
Fair Value of Plan Assets, Ending			(150)		$ (131.2)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets, Beginning		$ (150)	$ (131.2)
[1]	Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment.
[2]	Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E.
[3]	Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.
[4]	"Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E.
[5]	Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.
[6]	GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[7]	GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[8]	This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher.
[9]	This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher.
[10]	This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.
[11]	This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.

Retirement Plans and Postreti_4

Retirement Plans and Postretirement Benefit Plans Postretirement Benefit Plans (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020		Dec. 31, 2019
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions		$ 40	$ 20	$ 20
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Level 3 Asset Value, Beginning of Period		33.4	34.8
Interest income			0.8
Dividend income			0.6
Unrealized gains			0.6
Realized losses			0.4
Administrative expenses and charges			(0.1)
Claims paid			(3.7)
Level 3 Asset Value, End of Period			$ 33.4	$ 34.8
Postretirement Plan, Expected Future Benefit Payments, Next Twelve Months						$ 11.9
Postretirement Plan, Expected Future Benefit Payments, Year Two						11.8
Postretirement Plan, Expected Future Benefit Payments, Year Three						11.4
Postretirement Plan, Expected Future Benefit Payments in Year Four						10
Postretirement Plan, Expected Future Benefit Payments, Year Five						9.5
Postretirement Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter						40.9
Postemployment Benefits Liability						$ 2.2		$ 2.1
Ultimate Health Care Cost Trend Rate						4.50%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate					4.00%	3.50%		4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate			4.00%	4.00%	4.00%
Defined Contribution Plan, Cost			$ 18.2	$ 14.4	$ 13.2
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay			5.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match			200.00%
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		33.4	$ 33.4	34.8		$ 33.4		$ 34.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Claims Paid			3.7
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Administrative Expenses and Charges			0.1
Unrealized gains			0.6
Interest income			0.8
Dividend income			0.6
Og and E [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions			10	5
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Postretirement Plan, Expected Future Benefit Payments, Next Twelve Months						9.4
Postretirement Plan, Expected Future Benefit Payments, Year Two						9.3
Postretirement Plan, Expected Future Benefit Payments, Year Three						8.9
Postretirement Plan, Expected Future Benefit Payments in Year Four						7.7
Postretirement Plan, Expected Future Benefit Payments, Year Five						7.3
Postretirement Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter						31
Postemployment Benefits Liability						1.8		1.7
Defined Contribution Plan, Cost			14.3	11	9.8
Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			1.2
Fair Value of Plan Assets, Ending				1.2
Fair Value, Inputs, Level 1 [Member] | Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			1.2
Fair Value of Plan Assets, Ending				1.2
Fair Value, Inputs, Level 3 [Member] | Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning			0
Fair Value of Plan Assets, Ending				0
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		654.6	616.1	615.9
Service cost			13.2	12.9	14.9
Interest cost			17	20.7	23.8
Plan settlements			(42.8)	(83.1)
Actuarial losses			57.7	64.3
Benefit Obligation, Ending			654.6	616.1	615.9
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		570.3	530.3	522.8
Actual return on plans' assets			77	85.2
Employer contributions			20	20
Plan settlements			(42.8)	(83.1)
Fair Value of Plan Assets, Ending			570.3	530.3	522.8
Funded Status of Plan						$ (84.3)		$ (85.8)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			13.2	12.9	14.9
Interest cost			17	20.7	23.8
Expected return on plan assets			(37.6)	(36.1)	(44.1)
Amortization of unrecognized prior service cost	[1]		0	0	0
Curtailment			0	0	0
Settlement cost			14.1	27.6	25.1
Net periodic benefit cost			31.4	42.4	35.9
Amount paid by unconsolidated affiliates	[2]		2	2.9	2.5
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			29.4	39.5	33.4
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Capitalized Portion of Net Periodic Benefit Cost			$ 3.8	$ 3.6	$ 3.8
Assumptions Used Calculating Benefit Obligation, Discount Rate					4.20%	2.30%		3.15%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate			2.88%	3.63%	3.73%
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets			7.50%	7.50%	7.50%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase					4.20%	4.20%		4.20%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase			4.20%	4.20%	4.20%
Defined Benefit Plan, Benefit Obligation, Benefits Paid			$ (14.2)	$ (14.6)
Defined Benefit Plan, Plan Assets, Benefits Paid			14.2	14.6
Accumulated Benefit Obligation						$ 610.8		$ 563.3
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0	0
Plan curtailments			0	0
Pension Plan [Member] | Og and E [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		484.1	462	453.6
Service cost			9.2	9	$ 9.8
Interest cost			12.6	15.6	17.6
Plan settlements			(33.5)	(45.6)
Actuarial losses			41	42.1
Benefit Obligation, Ending			484.1	462	453.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		420.3	399.1	387.6
Actual return on plans' assets			57	64.8
Employer contributions			10	5
Plan settlements			(33.5)	(45.6)
Fair Value of Plan Assets, Ending			420.3	399.1	387.6
Funded Status of Plan						(63.8)		(62.9)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			9.2	9	9.8
Interest cost			12.6	15.6	17.6
Expected return on plan assets			(27.9)	(27.6)	(33.1)
Amortization of unrecognized prior service cost			0	0	0
Curtailment			0	0	0
Settlement cost			11.4	16.4	19.4
Net periodic benefit cost			22.5	26.3	25.8
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			28.4	30.8	31.5
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Capitalized Portion of Net Periodic Benefit Cost			3.1	3	3.2
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(12.3)	(12.7)
Defined Benefit Plan, Plan Assets, Benefits Paid			12.3	12.7
Accumulated Benefit Obligation						454.7		425.8
Plan curtailments			0	0
Pension Plan [Member] | Equity Funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[3]	25.4	23.9
Fair Value of Plan Assets, Ending	[3]		25.4	23.9
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Alternative Investment						25.4	[4],[5]	23.9	[3],[6]
Pension Plan [Member] | Money market funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		8.8	2.4
Fair Value of Plan Assets, Ending			8.8	2.4
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Alternative Investment						$ 8.8	[4]	$ 2.4	[6]
Pension Plan [Member] | Total Plan assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		570.3	530.3
Fair Value of Plan Assets, Ending			570.3	530.3
Pension Plan [Member] | Total Plan assets [Member] | Og and E [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		420.3	399.1
Fair Value of Plan Assets, Ending			420.3	399.1
Pension Plan [Member] | Plan Assets Attributable to Affiliates
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(150)	(131.2)
Fair Value of Plan Assets, Ending			(150)	(131.2)
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[3]	0	0
Fair Value of Plan Assets, Ending	[3]		0	0
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Money market funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[3]	0	0
Fair Value of Plan Assets, Ending	[3]		0	0
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Money market funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0	0
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0	0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		144.5	136.5	135.8
Service cost			0.2	0.2	0.3
Interest cost			4.2	5.6	5.4
Actuarial losses			7.3	2.9
Benefit Obligation, Ending			144.5	136.5	135.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		47.6	47	45.3
Actual return on plans' assets			1.2	4.6
Employer contributions			7.1	5.1
Fair Value of Plan Assets, Ending			47.6	47	45.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.2	0.2	0.3
Interest cost			4.2	5.6	5.4
Expected return on plan assets			(1.8)	(1.9)	(2)
Amortization of unrecognized prior service cost	[1]		(8.4)	(8.4)	(8.4)
Curtailment			(1.5)	0	0
Net periodic benefit cost			(2.3)	(2.5)	(0.9)
Amount paid by unconsolidated affiliates	[7]		(0.7)	(0.6)	(0.5)
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			(1.6)	(1.9)	(0.4)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Capitalized Portion of Net Periodic Benefit Cost			$ 0.2	$ 0.2	$ 0.2
Assumptions Used Calculating Benefit Obligation, Discount Rate					4.30%	2.45%		3.25%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate			3.25%	4.30%	3.70%
Health Care Cost Trend Rate Assumed for Next Fiscal Year						6.75%
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets			4.00%	4.00%	4.00%
Defined Benefit Plan, Benefit Obligation, Benefits Paid			$ (11)	$ (12.1)
Defined Benefit Plan, Plan Assets, Benefits Paid			11	12.1
Accumulated Benefit Obligation						$ 96.9		$ 89.5
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0	0
Plan curtailments			4	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Og and E [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		109.5	104.7	104.8
Service cost			0.2	0.2	$ 0.2
Interest cost			3.2	4.3	4.2
Actuarial losses			4.5	2.2
Benefit Obligation, Ending			109.5	104.7	104.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		42.7	41.9	40.6
Actual return on plans' assets			1.1	4
Employer contributions			5.9	4.1
Fair Value of Plan Assets, Ending			42.7	41.9	40.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.2	0.2	0.2
Interest cost			3.2	4.3	4.2
Expected return on plan assets			(1.7)	(1.7)	(1.8)
Amortization of unrecognized prior service cost	[1]		(6.1)	(6.1)	(6.1)
Curtailment			(1.3)	0	0
Net periodic benefit cost			(1)	(1.2)	0.3
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			(1.5)	(1.8)	(0.4)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Capitalized Portion of Net Periodic Benefit Cost			0.1	0.1	0.1
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(8.6)	(9.8)
Defined Benefit Plan, Plan Assets, Benefits Paid			8.6	9.8
Accumulated Benefit Obligation						66.8		62.8
Plan curtailments			3.1	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Group Retiree Medical Insurance Contract [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		33.4	34.8
Fair Value of Plan Assets, Ending			33.4	34.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Equity Mutual Funds Investment [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		10.8	10.9
Fair Value of Plan Assets, Ending			10.8	10.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		3.4
Fair Value of Plan Assets, Ending			3.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		14.2	12.1
Fair Value of Plan Assets, Ending			14.2	12.1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member] | Group Retiree Medical Insurance Contract [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Equity Mutual Funds Investment [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		10.8	10.9
Fair Value of Plan Assets, Ending			10.8	10.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member] | Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		3.4
Fair Value of Plan Assets, Ending			3.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		33.4	34.8
Fair Value of Plan Assets, Ending			33.4	34.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member] | Group Retiree Medical Insurance Contract [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		33.4	34.8
Fair Value of Plan Assets, Ending			33.4	34.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Equity Mutual Funds Investment [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0
Fair Value of Plan Assets, Ending			0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member] | Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0
Fair Value of Plan Assets, Ending			0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		47.6	46.9
Fair Value of Plan Assets, Ending			47.6	46.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member] | Og and E [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		42.7	41.9
Fair Value of Plan Assets, Ending			42.7	41.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1, 2 and 3 [Member] | OGE Energy [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(4.9)	(5)
Fair Value of Plan Assets, Ending			(4.9)	(5)
Other Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		7.8	10.3	9.6
Service cost			0.8	0.5	0.4
Interest cost			0.2	0.4	0.3
Plan settlements			(5.3)	(1.2)
Actuarial losses			1.6	0.7
Benefit Obligation, Ending			7.8	10.3	9.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0	0	0
Actual return on plans' assets			0	0
Employer contributions			5.3	1.2
Plan settlements			(5.3)	(1.2)
Fair Value of Plan Assets, Ending			0	0	0
Funded Status of Plan						(7.8)		(10.3)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.8	0.5	0.4
Interest cost			0.2	0.4	0.3
Expected return on plan assets			0	0	0
Amortization of unrecognized prior service cost	[1]		0	0	0.1
Curtailment			0.2	0	0
Settlement cost			2.7	0.5	1
Net periodic benefit cost			4.4	1.9	2.5
Amount paid by unconsolidated affiliates	[2]		0.1	0.1	0.1
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			4.3	1.8	2.4
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Benefits Paid			0	0
Defined Benefit Plan, Plan Assets, Benefits Paid			0	0
Accumulated Benefit Obligation						6.9		8.1
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0	0.3
Plan curtailments			0.2	0
Other Pension Plan [Member] | Og and E [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		3	6.1	6
Service cost			0.1	0.2	0.2
Interest cost			0.1	0.2	0.2
Plan settlements			(4.5)	(0.9)
Actuarial losses			1.2	0.6
Benefit Obligation, Ending			3	6.1	6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		$ 0	0	0
Actual return on plans' assets			0	0
Employer contributions			4.5	0.9
Plan settlements			(4.5)	(0.9)
Fair Value of Plan Assets, Ending			0	0	0
Funded Status of Plan						(3)		(6.1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.1	0.2	0.2
Interest cost			0.1	0.2	0.2
Expected return on plan assets			0	0	0
Amortization of unrecognized prior service cost			0	0	0
Curtailment			0	0	0
Settlement cost			2.4	0.5	0.4
Net periodic benefit cost			3	1.2	1.3
Net Periodic Benefit Cost, Net of Unconsolidated Affiliates			4.3	1.7	2.5
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Benefits Paid			0	0
Defined Benefit Plan, Plan Assets, Benefits Paid			0	0
Accumulated Benefit Obligation						$ 2.9		$ 4.8
Plan curtailments			0	0
OKLAHOMA | Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement cost	[8]		21.6	17.9	22.1
OKLAHOMA | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement cost			$ 1.4	$ 0	$ 0
[1]	Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment.
[2]	Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E.
[3]	This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.
[4]	GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[5]	This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.
[6]	GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[7]	"Amount paid by unconsolidated affiliates" is only applicable to OGE Energy. "Amount allocated from OGE Energy" is only applicable to OG&E.
[8]	Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.

Report of Business Segments (De

Report of Business Segments (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Operating revenues		$ 2,122.3		$ 2,231.6	$ 2,270.3
Cost of sales		644.6		786.9	892.5
Other operation and maintenance		462.8		491.8	474.6
Depreciation and amortization		391.3		355	321.6
Taxes other than income		101.4		93.6	92
Operating income (loss)		522.2		504.3	489.6
Equity in earnings of unconsolidated affiliates	[1]	(668)	[2]	113.9	152.8
Other income (expense)		3.2		(6.9)	11.3
Interest expense		158.5		147.9	156
Income tax expense (benefit)		(127.4)		29.8	72.2
NET INCOME (LOSS)		(173.7)		433.6	425.5
Investment in unconsolidated affiliates		397.4		1,151.5	1,177.5
Total assets		10,718.8		11,024.3	10,748.6
Capital expenditures		650.5		635.5	573.6
Equity Method Investment, Other than Temporary Impairment		780		0	0
Electric Utility [Member]
Segment Reporting Information [Line Items]
Operating revenues		2,122.3		2,231.6	2,270.3
Cost of sales		644.6		786.9	892.5
Other operation and maintenance		464.4		492.5	473.8
Depreciation and amortization		391.3		355	321.6
Taxes other than income		97.2		89.5	88.2
Operating income (loss)		524.8		507.7	494.2
Equity in earnings of unconsolidated affiliates		0	[2]	0	0
Other income (expense)		4.1		3.1	25.6
Interest expense		154.8		140.5	151.8
Income tax expense (benefit)		34.7		20.1	40
NET INCOME (LOSS)		339.4		350.2	328
Investment in unconsolidated affiliates		0		0	0
Total assets		10,489		10,076.6	9,704.5
Capital expenditures		650.5		635.5	573.6
Natural Gas Midstream Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues		0		0	0
Cost of sales		0		0	0
Other operation and maintenance		1.7		2.8	1.4
Depreciation and amortization		0		0	0
Taxes other than income		0.4		0.4	0.6
Operating income (loss)		(2.1)		(3.2)	(2)
Equity in earnings of unconsolidated affiliates		(668)	[2]	113.9	152.8
Other income (expense)		(2.9)		(8.6)	(4.9)
Interest expense		0		0	0
Income tax expense (benefit)		(158)		20.7	37.1
NET INCOME (LOSS)		(515)		81.4	108.8
Investment in unconsolidated affiliates		374.3		1,132.9	1,166.6
Total assets		378.1		1,135.4	1,169.8
Capital expenditures		0		0	0
Other Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues		0		0	0
Cost of sales		0		0	0
Other operation and maintenance		(3.3)		(3.5)	(0.6)
Depreciation and amortization		0		0	0
Taxes other than income		3.8		3.7	3.2
Operating income (loss)		(0.5)		(0.2)	(2.6)
Equity in earnings of unconsolidated affiliates		0	[2]	0	0
Other income (expense)		3.6		2.2	(3.4)
Interest expense		5.3		11	10.2
Income tax expense (benefit)		(4.1)		(11)	(4.9)
NET INCOME (LOSS)		1.9		2	(11.3)
Investment in unconsolidated affiliates		23.1		18.6	10.9
Total assets		116.4		107	184.8
Capital expenditures		0		0	0
Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues		0		0	0
Cost of sales		0		0	0
Other operation and maintenance		0		0	0
Depreciation and amortization		0		0	0
Taxes other than income		0		0	0
Operating income (loss)		0		0	0
Equity in earnings of unconsolidated affiliates		0	[2]	0	0
Other income (expense)		(1.6)		(3.6)	(6)
Interest expense		(1.6)		(3.6)	(6)
Income tax expense (benefit)		0		0	0
NET INCOME (LOSS)		0		0	0
Investment in unconsolidated affiliates		0		0	0
Total assets		(264.7)		(294.7)	(310.5)
Capital expenditures		$ 0		$ 0	$ 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.

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Millions		12 Months Ended
		Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months		$ 130.1
Operating Leases, Future Minimum Payments, Due in Two Years		108.4
Operating Leases, Future Minimum Payments, Due in Three Years		114.3
Operating Leases, Future Minimum Payments, Due in Four Years		128.4
Operating Leases, Future Minimum Payments, Due in Five Years		114
Operating Leases, Future Minimum Payments Due		595.2
Utilities Operating Expense, Purchased Power under Long-term Contracts		57.3	$ 57.7	$ 57.6
OG&E minimum fuel purchase commitments [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		235.9
Purchase Obligation, Due in Next Twelve Months		72.5
Unrecorded Unconditional Purchase Obligation, Due within Two Years		50.4
Unrecorded Unconditional Purchase Obligation, Due within Three Years		50.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years		36.7
Unrecorded Unconditional Purchase Obligation, Due within Five Years		25.9
OG&E expected wind purchase commitments [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		280.3
Purchase Obligation, Due in Next Twelve Months		55.2
Unrecorded Unconditional Purchase Obligation, Due within Two Years		55.6
Unrecorded Unconditional Purchase Obligation, Due within Three Years		56
Unrecorded Unconditional Purchase Obligation, Due within Four Years		56.6
Unrecorded Unconditional Purchase Obligation, Due within Five Years		56.9
OG&E long-term service agreement commitments [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		79
Purchase Obligation, Due in Next Twelve Months		2.4
Unrecorded Unconditional Purchase Obligation, Due within Two Years		2.4
Unrecorded Unconditional Purchase Obligation, Due within Three Years		7.9
Unrecorded Unconditional Purchase Obligation, Due within Four Years		35.1
Unrecorded Unconditional Purchase Obligation, Due within Five Years		31.2
OG&E total cogeneration payments [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts			14.7	112.4
OG&E capacity payments [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts			7.4	60
CPV Keenan [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts		27.5	27.2	27
Edison Mission Energy [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts		22.8	23.1	21.7
NextEra Energy [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts		7	7.4	6.8
FPL Energy [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts	[1]	$ 0	$ 0	$ 2.1
OG&E long-term service agreement commitments [Member] | McClain Plant [Member]
Loss Contingencies [Line Items]
Factored-Fired Hours		128,000
Factored-Fired Starts		4,800
OG&E long-term service agreement commitments [Member] | Redbud Plant [Member]
Loss Contingencies [Line Items]
Factored-Fired Hours		144,000
Factored-Fired Starts		4,500
Additional Factored-Fired Hours		24,000
Maximum [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Maximum		$ 1,000
[1]	OG&E's purchased power contract with FPL Energy for 50 MWs expired in 2018.

Rate Matters and Regulation (De

Rate Matters and Regulation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Estimated Refund to SPP	$ 13
Investment in Grid Enhancement	800
Plant Investments For Customers	28
Other Commitment	1,000
Minimum [Member]
Lost Revenue on Plant Investments for Customers	14.5
Loss Contingency, Range of Possible Loss, Maximum	800
Maximum [Member]
Lost Revenue on Plant Investments for Customers	21.7
Loss Contingency, Range of Possible Loss, Maximum	1,000
In Favor Cooperatives [Member]
Plant Investments For Customers	11.7
In Favor Cooperatives [Member] | Minimum [Member]
Lost Revenue on Plant Investments for Customers	1.4
In Favor Cooperatives [Member] | Maximum [Member]
Lost Revenue on Plant Investments for Customers	2.3
Impact to Company [Member]
Estimated Refund to SPP	5
Customer Impact [Member]
Estimated Refund to SPP	$ 8
Oklahoma Corporation Commission [Member]
OG&E's Jurisdictional Revenues	86.00%
Arkansas Public Service Commission [Member]
OG&E's Jurisdictional Revenues	8.00%
Federal Energy Regulatory Commission [Member]
OG&E's Jurisdictional Revenues	6.00%
Arkansas Environmental [Member]
Customer Refund Amount	$ 5.3
Grid Enhancement
OCC Revenue Requirement	7
ARKANSAS
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 6.7	$ 5.2

Schedule II (Details)

Schedule II (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Beginning Balance		$ 1.5	$ 1.7	$ 1.5
Valuation Allowances and Reserves, Charged to Cost and Expense		3	2.2	3.4
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	[1]	1.9	2.4	3.2
Valuation Allowances and Reserves, Ending Balance		$ 2.6	$ 1.5	$ 1.7
[1]	Uncollectible accounts receivable written off, net of recoveries.

Uncategorized Items - oge-20201

Label	Element	Value
Stock Issued During Period, Value, New Issues	us-gaap_StockIssuedDuringPeriodValueNewIssues	$ (14,700,000)