Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2019

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.

	June 30,		December 31,
(In millions)	2019		2018
REGULATORY ASSETS
Current:
Fuel clause under recoveries	$	30.7	$	2.0
Cogeneration credit rider over credit (A)	8.2		—
Production tax credit rider over credit (A)	4.1		6.9
Oklahoma demand program rider under recovery (A)	—		6.4
Other (A)	5.1		3.2
Total current regulatory assets	$	48.1	$	18.5
Non-current:
Benefit obligations regulatory asset	$	172.3	$	188.2
Deferred storm expenses	43.6		36.5
Smart Grid	22.1		25.6
Sooner Dry Scrubbers	21.0		4.5
Unamortized loss on reacquired debt	11.0		11.4
Arkansas deferred pension expenses	7.7		6.8
Other	12.3		12.8
Total non-current regulatory assets	$	290.0	$	285.8
REGULATORY LIABILITIES
Current:
Reserve for tax refund and interim surcharge (B)	$	17.7	$	15.4
SPP cost tracker over recovery (B)	8.0		16.8
Oklahoma demand program rider over recovery (B)	6.2		—
Transmission cost recovery rider over recovery (B)	1.1		2.7
Fuel clause over recoveries	0.1		0.3
Other (B)	3.2		1.4
Total current regulatory liabilities	$	36.3	$	36.6
Non-current:
Income taxes refundable to customers, net	$	921.6	$	937.1
Accrued removal obligations, net	312.9		308.1
Pension tracker	2.2		18.7
Other	6.3		6.8
Total non-current regulatory liabilities	$	1,243.0	$	1,270.7

(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 six months ended June 30, 2019 and 2018. All amounts below are presented net of tax.

	Pension Plan and Restoration of Retirement Income Plan					Postretirement Benefit Plans
(In millions)	Net Income  (Loss)			Prior Service Cost (Credit)		Net Income (Loss)			Prior Service Cost (Credit)			Total
Balance at December 31, 2018	$	(38.8	)	$	—	$	4.6		$	5.3		$	(28.9	)
Amounts reclassified from accumulated other comprehensive income (loss)	1.7			—		(0.1		)	(0.9		)	0.7
Settlement cost	7.1			—		—			—			7.1
Balance at June 30, 2019	$	(30.0	)	$	—	$	4.5		$	4.4		$	(21.1	)

	Pension Plan and Restoration of Retirement Income Plan					Postretirement Benefit Plans
(In millions)	Net Income  (Loss)			Prior Service Cost (Credit)		Net Income		Prior Service Cost (Credit)			Total
Balance at December 31, 2017	$	(32.7	)	$	—	$	2.5	$	7.0		$	(23.2	)
Amounts reclassified from accumulated other comprehensive income (loss)	1.7			—		—		(0.8		)	0.9
Balance at June 30, 2018	$	(31.0	)	$	—	$	2.5	$	6.2		$	(22.3	)

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 during the three and six months ended June 30, 2019 and 2018.

Details about Accumulated Other Comprehensive Income (Loss) Components	Amount Reclassified from Accumulated Other Comprehensive Income (Loss)												Affected Line Item in the Condensed Consolidated Statements of Income
	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In millions)	2019			2018			2019			2018
Amortization of Pension Plan and Restoration of Retirement Income Plan items:
Actuarial losses (A)	$	(1.3	)	$	(1.3	)	$	(2.2	)	$	(2.2	)	Other Net Periodic Benefit Expense
Settlement cost (A)	(0.6		)	—			(9.4		)	—			Other Net Periodic Benefit Expense
	(1.9		)	(1.3		)	(11.6		)	(2.2		)	Income Before Taxes
	(0.4		)	(0.3		)	(2.8		)	(0.5		)	Income Tax Expense
	$	(1.5	)	$	(1.0	)	$	(8.8	)	$	(1.7	)	Net Income
Amortization of postretirement benefit plans items:
Prior service credit (A)	$	0.5		$	0.5		$	1.1		$	1.1		Other Net Periodic Benefit Expense
Actuarial gains (A)	0.1			—			0.1			—			Other Net Periodic Benefit Expense
	0.6			0.5			1.2			1.1			Income Before Taxes
	0.1			0.2			0.2			0.3			Income Tax Expense
	$	0.5		$	0.3		$	1.0		$	0.8		Net Income
Total reclassifications for the period, net of tax	$	(1.0	)	$	(0.7	)	$	(7.8	)	$	(0.9	)	Net Income

(A)

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