Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2021

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.

	September 30,		December 31,
(In millions)	2021		2020
REGULATORY ASSETS
Current:
Fuel clause under recoveries	$	98.2	$	—
SPP cost tracker under recoveries (A)	7.7		7.0
Generation Capacity Replacement rider under recoveries (A)	1.7		4.4
Other (A)	7.7		8.4
Total current regulatory assets	$	115.3	$	19.8
Non-current:
Oklahoma Winter Storm Uri costs	$	756.3	$	—
Oklahoma deferred storm expenses	173.8		158.8
Benefit obligations regulatory asset	130.6		164.9
Arkansas Winter Storm Uri costs	91.0		—
Pension tracker	41.6		18.1
Sooner Dry Scrubbers	19.1		19.7
Arkansas deferred pension expenses	11.8		9.3
Unamortized loss on reacquired debt	9.1		9.7
COVID-19 impacts	8.0		6.4
Frontier Plant deferred expenses	7.1		6.4
Smart Grid	5.9		11.2
Other	10.6		11.1
Total non-current regulatory assets	$	1,264.9	$	415.6
REGULATORY LIABILITIES
Current:
Oklahoma energy efficiency rider over recoveries (B)	$	4.7	$	1.5
Fuel clause over recoveries	—		28.6
Other (B)	1.6		5.0
Total current regulatory liabilities	$	6.3	$	35.1
Non-current:
Income taxes refundable to customers, net	$	938.8	$	867.4
Accrued removal obligations, net	305.1		316.8
Other	3.8		4.7
Total non-current regulatory liabilities	$	1,247.7	$	1,188.9

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

(B)Included in Other Current Liabilities in the balance sheets.

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

The following tables present changes in the components of accumulated other comprehensive income (loss) attributable to OGE Energy during the nine months ended September 30, 2021 and 2020. All amounts below are presented net of tax.

(In millions)	Pension Plan and Restoration of Retirement Income Plan		Postretirement Benefit Plans		Other Comprehensive Gain (Loss) from Unconsolidated Affiliates		Total
Balance at December 31, 2020	$	(34.1)	$	3.3	$	(1.3)	$	(32.1)
Other comprehensive income before reclassifications	—		—		0.6		0.6
Amounts reclassified from accumulated other comprehensive income (loss)	1.3		(0.9)		—		0.4
Settlement cost	4.8		—		—		4.8
Balance at September 30, 2021	$	(28.0)	$	2.4	$	(0.7)	$	(26.3)

(In millions)	Pension Plan and Restoration of Retirement Income Plan		Postretirement Benefit Plans		Other Comprehensive Loss from Unconsolidated Affiliates		Total
Balance at December 31, 2019	$	(35.1)	$	7.8	$	(0.6)	$	(27.9)
Other comprehensive loss before reclassifications	—		—		(0.9)		(0.9)
Amounts reclassified from accumulated other comprehensive income (loss)	2.9		(1.3)		—		1.6
Settlement cost	1.5		—		—		1.5
Balance at September 30, 2020	$	(30.7)	$	6.5	$	(1.5)	$	(25.7)

Schedule of Amounts Reclassified out of Accumulated Other Comprehensive Income [Table Text Block]

The following table presents significant amounts reclassified out of accumulated other comprehensive income (loss) attributable to OGE Energy by the respective line items in net income (loss) during the three and nine months ended September 30, 2021 and 2020.

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
	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(In millions)	2021		2020		2021		2020
Amortization of Pension Plan and Restoration of Retirement Income Plan items:
Actuarial losses	$	(0.6)	$	(1.2)	$	(1.8)	$	(3.8)	(A)
Prior service cost	(0.1)		—		(0.1)		—		(A)
Settlement cost	(1.4)		(1.8)		(6.7)		(2.1)		(A)
	(2.1)		(3.0)		(8.6)		(5.9)		Income (Loss) Before Taxes
	(0.5)		(0.8)		(2.5)		(1.5)		Income Tax Expense (Benefit)
	$	(1.6)	$	(2.2)	$	(6.1)	$	(4.4)	Net Income (Loss)
Amortization of postretirement benefit plans items:
Prior service credit	$	0.4	$	0.6	$	1.3	$	1.7	(A)
Actuarial gains (losses)	—		—		(0.1)		0.1		(A)
	0.4		0.6		1.2		1.8		Income (Loss) Before Taxes
	0.1		0.2		0.3		0.5		Income Tax Expense (Benefit)
	$	0.3	$	0.4	$	0.9	$	1.3	Net Income (Loss)
Total reclassifications for the period, net of tax	$	(1.3)	$	(1.8)	$	(5.2)	$	(3.1)	Net Income (Loss)

(A)These accumulated other comprehensive income (loss) components are included in the computation of net periodic benefit cost (see Note 12 for additional information).