Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Regulatory Assets and Liabilities [Table Text Block]

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

	September 30,		December 31,
(In millions)	2020		2019
REGULATORY ASSETS
Current:
SPP cost tracker under recovery (A)	$	4.6	$	—
Generation Capacity Replacement rider under recovery (A)	1.2		3.7
Fuel clause under recoveries	—		39.5
Other (A)	9.7		5.5
Total current regulatory assets	$	15.5	$	48.7
Non-current:
Benefit obligations regulatory asset	$	150.2	$	167.2
Deferred storm expenses	70.2		65.5
Sooner Dry Scrubbers	19.9		20.6
Smart Grid	13.1		18.4
Unamortized loss on reacquired debt	9.9		10.6
Arkansas deferred pension expenses	8.4		8.0
Pension tracker	8.1		2.3
COVID-19 deferred expenses	4.9		—
Other	16.9		13.4
Total non-current regulatory assets	$	301.6	$	306.0
REGULATORY LIABILITIES
Current:
Fuel clause over recoveries	$	39.6	$	4.8
Oklahoma demand program rider over recovery (B)	5.8		2.0
Reserve for tax refund and interim surcharge (B)	1.3		12.7
SPP cost tracker over recovery (B)	—		2.6
Other (B)	4.9		6.9
Total current regulatory liabilities	$	51.6	$	29.0
Non-current:
Income taxes refundable to customers, net	$	875.5	$	899.2
Accrued removal obligations, net	318.9		318.5
Other	5.0		5.8
Total non-current regulatory liabilities	$	1,199.4	$	1,223.5

(A)Included in Other Current Assets in the Condensed Consolidated Balance Sheets.

(B)Included in Other Current Liabilities in the Condensed Consolidated Balance Sheets.

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

The following tables summarize changes in the components of accumulated other comprehensive income (loss) attributable to the Company during the nine months ended September 30, 2020 and 2019. All amounts below are presented net of tax.

(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)

(In millions)	Pension Plan and Restoration of Retirement Income Plan		Postretirement Benefit Plans		Other Comprehensive Loss from Unconsolidated Affiliates		Total
Balance at December 31, 2018	$	(38.8)	$	9.9	$	—	$	(28.9)
Other comprehensive loss before reclassifications	—		—		(0.6)		(0.6)
Amounts reclassified from accumulated other comprehensive income (loss)	2.6		(1.4)		—		1.2
Settlement cost	7.9		—		—		7.9
Balance at September 30, 2019	$	(28.3)	$	8.5	$	(0.6)	$	(20.4)

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

The following table summarizes significant amounts reclassified out of accumulated other comprehensive income (loss) by the respective line items in net income (loss) during the three and nine months ended September 30, 2020 and 2019.

Details about Accumulated Other Comprehensive Income (Loss) Components	Amount Reclassified from Accumulated Other Comprehensive Income (Loss)								Affected Line Item in the Consolidated Statements of Income
	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(In millions)	2020		2019		2020		2019
Amortization of Pension Plan and Restoration of Retirement Income Plan items:
Actuarial losses	$	(1.2)	$	(1.2)	$	(3.8)	$	(3.4)	(A)
Settlement cost	(1.8)		(1.1)		(2.1)		(10.5)		(A)
	(3.0)		(2.3)		(5.9)		(13.9)		Income (Loss) Before Taxes
	(0.8)		(0.6)		(1.5)		(3.4)		Income Tax Expense (Benefit)
	$	(2.2)	$	(1.7)	$	(4.4)	$	(10.5)	Net Income (Loss)
Amortization of postretirement benefit plans items:
Prior service credit	$	0.6	$	0.6	$	1.7	$	1.7	(A)
Actuarial gains	—		—		0.1		0.1		(A)
	0.6		0.6		1.8		1.8		Income (Loss) Before Taxes
	0.2		0.2		0.5		0.4		Income Tax Expense (Benefit)
	$	0.4	$	0.4	$	1.3	$	1.4	Net Income (Loss)
Total reclassifications for the period, net of tax	$	(1.8)	$	(1.3)	$	(3.1)	$	(9.1)	Net Income (Loss)

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