Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 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.

	March 31,		December 31,
(In millions)	2020		2019
REGULATORY ASSETS
Current:
Generation Capacity Replacement rider under recovery (A)	$	4.6	$	3.7
Fuel clause under recoveries	—		39.5
Other (A)	8.2		5.5
Total current regulatory assets	$	12.8	$	48.7
Non-current:
Benefit obligations regulatory asset	$	165.2	$	167.2
Deferred storm expenses	63.9		65.5
Sooner Dry Scrubbers	20.4		20.6
Smart Grid	16.6		18.4
Unamortized loss on reacquired debt	10.4		10.6
Arkansas deferred pension expenses	7.8		8.0
Pension tracker	0.9		2.3
Other	14.8		13.4
Total non-current regulatory assets	$	300.0	$	306.0
REGULATORY LIABILITIES
Current:
Fuel clause over recoveries	$	15.6	$	4.8
Reserve for tax refund and interim surcharge (B)	4.8		12.7
Oklahoma demand program rider over recovery (B)	4.4		2.0
SPP cost tracker over recovery (B)	—		2.6
Other (B)	5.6		6.9
Total current regulatory liabilities	$	30.4	$	29.0
Non-current:
Income taxes refundable to customers, net	$	890.9	$	899.2
Accrued removal obligations, net	319.7		318.5
Other	5.5		5.8
Total non-current regulatory liabilities	$	1,216.1	$	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 three months ended March 31, 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 income (loss) before reclassifications	—		—		(1.3)		(1.3)
Amounts reclassified from accumulated other comprehensive income (loss)	0.8		(0.4)		—		0.4
Balance at March 31, 2020	$	(34.3)	$	7.4	$	(1.9)	$	(28.8)

(In millions)	Pension Plan and Restoration of Retirement Income Plan		Postretirement Benefit Plans		Total
Balance at December 31, 2018	$	(38.8)	$	9.9	$	(28.9)
Amounts reclassified from accumulated other comprehensive income (loss)	0.7		(0.5)		0.2
Settlement cost	6.6		—		6.6
Balance at March 31, 2019	$	(31.5)	$	9.4	$	(22.1)

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 months ended March 31, 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
	March 31,
(In millions)	2020		2019
Amortization of Pension Plan and Restoration of Retirement Income Plan items:
Actuarial losses	$	(1.1)	$	(0.9)	(A)
Settlement cost	—		(8.8)		(A)
	(1.1)		(9.7)		Income (Loss) Before Taxes
	(0.3)		(2.4)		Income Tax Expense (Benefit)
	$	(0.8)	$	(7.3)	Net Income (Loss)
Amortization of postretirement benefit plans items:
Prior service credit	$	0.6	$	0.6	(A)
	0.6		0.6		Income (Loss) Before Taxes
	0.2		0.1		Income Tax Expense (Benefit)
	$	0.4	$	0.5	Net Income (Loss)
Total reclassifications for the period, net of tax	$	(0.4)	$	(6.8)	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).