Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Regulatory Assets and Liabilities

The following table presents a summary of OG&E's regulatory assets and liabilities.

December 31 (In millions)	2023		2022
REGULATORY ASSETS
Current:
Oklahoma Energy Efficiency Rider under recoveries (A)	$	3.8	$	7.7
Oklahoma fuel clause under recoveries		—		474.3
Arkansas fuel clause under recoveries		—		40.6
Other (A)		2.7		4.7
Total current regulatory assets	$	6.5	$	527.3
Non-current:
Oklahoma deferred storm expenses	$	261.1	$	206.3
Pension tracker		91.9		57.2
Benefit obligations regulatory asset		89.4		119.7
Arkansas Winter Storm Uri costs		71.0		78.2
Sooner Dry Scrubbers		17.2		18.1
Arkansas deferred pension expenses		12.7		12.3
Unamortized loss on reacquired debt		7.2		8.0
COVID-19 impacts		6.8		7.7
Oklahoma SAP S/4 HANA deferred expenses		6.0		0.7
Frontier Plant deferred expenses		3.6		5.2
Other		10.7		10.9
Total non-current regulatory assets	$	577.6	$	524.3
REGULATORY LIABILITIES
Current:
Oklahoma fuel clause over recoveries	$	15.6	$	—
SPP cost tracker over recovery (B)		10.4		3.0
Arkansas fuel clause over recoveries		4.9		—
Other (B)		2.3		2.5
Total current regulatory liabilities	$	33.2	$	5.5
Non-current:
Income taxes refundable to customers, net	$	838.0	$	894.7
Accrued removal obligations, net		222.0		250.5
Other		1.6		1.9
Total non-current regulatory liabilities	$	1,061.6	$	1,147.1

(A)Included in Other Current Assets in the balance sheets.

Included in Other Current Liabilities in the balance sheets.

Summary of Components of Benefit Obligation

The following table presents a summary of the components of the benefit obligations regulatory asset.

December 31 (In millions)	2023		2022
Pension Plan and Restoration of Retirement Income Plan:
Net loss	$	75.9	$	110.0
Postretirement Benefit Plans:
Net loss		13.5		9.7
Total	$	89.4	$	119.7

Schedule of Jointly Owned Utility Plants

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, 2023 (In millions)	Percentage Ownership			Total Property, Plant and Equipment		Accumulated Depreciation		Net Property, Plant and Equipment
McClain Plant (A)		77	%	$	265.4	$	129.2	$	136.2
Redbud Plant (A)(B)		51	%	$	548.9	$	245.5	$	303.4

(A)Construction work in progress was $0.3 million and $2.0 million for the McClain and Redbud Plants, respectively.

(B)This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $83.8 million.

December 31, 2022 (In millions)	Percentage Ownership			Total Property, Plant and Equipment		Accumulated Depreciation		Net Property, Plant and Equipment
McClain Plant (A)		77	%	$	261.9	$	119.4	$	142.5
Redbud Plant (A)(B)		51	%	$	542.1	$	225.2	$	316.9

(A)Construction work in progress was $0.7 million and $1.5 million for the McClain and Redbud Plants, respectively.

(B)This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $78.3 million.

Summary of Property Plant and Equipment

The following tables present the Registrants' major classes of property, plant and equipment and related accumulated depreciation.

December 31, 2023 (In millions)	Total Property, Plant and Equipment		Accumulated Depreciation		Net Property, Plant and Equipment
OG&E:
Distribution assets	$	6,290.1	$	1,564.3	$	4,725.8
Electric generation assets (A)		5,295.9		2,081.0		3,214.9
Transmission assets (B)		3,306.7		707.6		2,599.1
Intangible plant		568.5		219.8		348.7
Other property and equipment		643.1		236.7		406.4
OG&E property, plant and equipment		16,104.3		4,809.4		11,294.9
Non-OG&E property, plant and equipment		6.1		—		6.1
Total OGE Energy property, plant and equipment	$	16,110.4	$	4,809.4	$	11,301.0

(A)This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $83.8 million.

(B)This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $1.1 million.

December 31, 2022 (In millions)	Total Property, Plant and Equipment		Accumulated Depreciation		Net Property, Plant and Equipment
OG&E:
Distribution assets	$	5,781.3	$	1,527.1	$	4,254.2
Electric generation assets (A)		5,188.1		1,982.7		3,205.4
Transmission assets (B)		3,180.5		667.9		2,512.6
Intangible plant		384.0		193.6		190.4
Other property and equipment		591.3		213.2		378.1
OG&E property, plant and equipment		15,125.2		4,584.5		10,540.7
Non-OG&E property, plant and equipment		6.1		—		6.1
Total OGE Energy property, plant and equipment	$	15,131.3	$	4,584.5	$	10,546.8

(A)This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $78.3 million.

(B)This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $1.0 million.

Schedule of Change in Asset Retirement Obligation

The following table presents changes to OG&E's asset retirement obligations during the years ended December 31, 2023 and 2022.

(In millions)	2023		2022
Balance at January 1	$	78.3	$	80.2
Accretion expense		0.7		0.6
Liabilities settled (A)		—		(2.5	)
Revisions in estimated cash flows (B)		2.3		—
Balance at December 31	$	81.3	$	78.3

(A) Asset retirement obligations were settled for asbestos removal at OG&E's generating facilities.

(B) Assumptions changed related to the estimated timing and estimated cost of the removal of asbestos at OG&E's generating facilities.

Summary of Accumulated Other Comprehensive Income (Loss) (Details)

The following table presents changes in the components of accumulated other comprehensive income (loss) attributable to OGE Energy during 2023 and 2022. All amounts below are presented net of tax.

	Pension Plan and Restoration of Retirement Income Plan						Postretirement Benefit Plans
(In millions)	Net Gain (Loss)			Prior Service Cost (Credit)			Net Gain (Loss)			Prior Service Cost (Credit)			Total
Balance at December 31, 2021	$	(24.9	)	$	(1.2	)	$	1.1		$	0.2		$	(24.8	)
Other comprehensive income (loss) before reclassifications		(7.6	)		—			5.5			—			(2.1	)
Amounts reclassified from accumulated other comprehensive income (loss)		1.4			0.2			—			(0.2	)		1.4
Settlement cost		13.6			—			—			—			13.6
Net current period other comprehensive income (loss)		7.4			0.2			5.5			(0.2	)		12.9
Balance at December 31, 2022		(17.5	)		(1.0	)		6.6			—			(11.9	)
Other comprehensive income (loss) before reclassifications		3.3			—			(0.8	)		—			2.5
Amounts reclassified from accumulated other comprehensive income (loss)		0.9			0.2			(0.1	)		—			1.0
Settlement cost		1.2			—			—			—			1.2
Net current period other comprehensive income (loss)		5.4			0.2			(0.9	)		—			4.7
Balance at December 31, 2023	$	(12.1	)	$	(0.8	)	$	5.7		$	—		$	(7.2	)

Reclassified Out of Accumulated Other Comprehensive Income (Loss)

The following table presents significant amounts reclassified out of accumulated other comprehensive income (loss) by the respective line items in net income during the years ended December 31, 2023 and 2022.

Details about Accumulated Other Comprehensive Income (Loss) Components	Amount Reclassified from Accumulated Other Comprehensive Income (Loss)						Affected Line Item in OGE Energy's Statements of Income
	Year Ended December 31,
(In millions)	2023			2022
Amortization of Pension Plan and Restoration of Retirement Income Plan items:
Actuarial losses	$	(1.1	)	$	(1.6	)	(A)
Prior service cost		(0.3	)		(0.3	)	(A)
Settlement cost		(1.6	)		(17.9	)	(A)
		(3.0	)		(19.8	)	Income Before Taxes
		(0.7	)		(4.6	)	Income Tax Expense
	$	(2.3	)	$	(15.2	)	Net Income
Amortization of postretirement benefit plans items:
Prior service credit	$	—		$	0.3		(A)
Actuarial gains		0.2			—		(A)
		0.2			0.3		Income Before Taxes
		0.1			0.1		Income Tax Expense
	$	0.1		$	0.2		Net Income
Total reclassifications for the period, net of tax	$	(2.2	)	$	(15.0	)	Net Income

(A)These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost (see Note 11 for additional information).

Reconciliation of Equity in Earnings (Losses) of Unconsolidated Affiliates

The following table presents a reconciliation of OGE Energy's equity in earnings of unconsolidated affiliates for the period of January 1, 2021 through December 2, 2021.

(In millions)
Enable net income used to calculate OGE Energy's equity in earnings	$	470.0
OGE Energy's percent ownership at period end		25.5	%
OGE Energy's portion of Enable net income	$	119.8
Amortization of basis difference and dilution recognition (A)		50.0
Equity in earnings of unconsolidated affiliates	$	169.8

(A)Includes loss on dilution, net of proportional basis difference recognition.

Schedule of Related Party Transactions

The following table presents summarized related party transactions between OG&E and Enable during the period of January 1, 2021 through December 2, 2021.

(In millions)
Operating revenues:
Electricity to power electric compression assets	$	13.3
Fuel, purchased power and direct transmission expense:
Natural gas transportation services	$	32.7
Natural gas sales	$	(33.5	)