Oklahoma Gas And Electric 10-K 27 Feb 20 2019 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019
Document Information [Line Items]
Entity Registrant Name	OKLAHOMA GAS AND ELECTRIC COMPANY
Entity Central Index Key	0000074145
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	40,378,745
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float		$ 0
Entity File Number	1-1097
Entity Tax Identification Number	73-0382390
Entity Address, Address Line One	321 North Harvey
Entity Address, Address Line Two	P.O. Box 321
Entity Address, City or Town	Oklahoma City
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	73101-0321
City Area Code	405
Local Phone Number	553-3000
Entity Interactive Data Current	Yes
Document Transition Report	false
Document Annual Report	true

STATEMENTS OF INCOME

STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,175.5	$ 2,211.7	$ 0
Revenues from Alternative Revenue Programs	56.1	58.6	0
Revenues	2,231.6	2,270.3	2,261.1
Cost of Goods and Services Sold	786.9	892.5	897.6
OPERATING EXPENSES
Other operation and maintenance	492.5	473.8	469.8
Depreciation and amortization	355	321.6	280.9
Taxes other than income	89.5	88.2	84.8
Operating expenses	937	883.6	835.5
OPERATING INCOME	507.7	494.2	528
OTHER INCOME (EXPENSE)
Allowance for equity funds used during construction	4.5	23.8	39.7
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	(1.2)	(8.9)	(16.3)
Other income	6.7	14.1	36.6
Other expense	(6.9)	(3.4)	(2.3)
Net other income	3.1	25.6	57.7
INTEREST EXPENSE
Interest on long-term debt	138.3	157.4	151.9
Allowance for borrowed funds used during construction	(2.8)	(11.7)	(18)
Interest on short-term debt and other interest charges	5	6.1	4.5
Interest expense	140.5	151.8	138.4
INCOME BEFORE TAXES	370.3	368	447.3
INCOME TAX EXPENSE	20.1	40	141.8
NET INCOME	350.2	328	305.5
Other comprehensive income, net of tax	0	0	0
COMPREHENSIVE INCOME	$ 350.2	$ 328	$ 305.5

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 350.2	$ 328	$ 305.5
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation and amortization	355	321.6	280.9
Deferred income taxes and investment tax credits, net	20.4	56.6	119.8
Allowance for equity funds used during construction	(4.5)	(23.8)	(39.7)
Stock-based compensation expense	4.9	4.6	3.1
Regulatory assets	(47.1)	(10.8)	3.7
Regulatory liabilities	(45.6)	(16.5)	(3.7)
Other assets	3.8	1.9	1.6
Other liabilities	8.4	0	(59.9)
Change in certain current assets and liabilities:
Accounts receivable and accrued unbilled revenues, net	17	19.5	(22.2)
Fuel, materials and supplies inventories	4.2	27.3	(5)
Fuel recoveries	(33)	(3.4)	53
Other current assets	5.9	23.1	29.7
Accounts payable	(30)	19	22.5
Income taxes payable - parent	(0.7)	(15.6)	92
Other current liabilities	(35.1)	72.5	(65.6)
Net Cash Provided from Operating Activities	573.8	804	715.7
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)	(635.5)	(573.6)	(824.1)
Proceeds from sale of assets	0	0.1	0.7
Net cash used in investing activities	(635.5)	(573.5)	(823.4)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	296.5	396	592.1
Changes in advances with parent	15.3	(191.4)	(189.3)
Payment of long-term debt	(250.1)	(250.1)	(125.1)
Dividends paid on common stock	0	(185)	(170)
Net cash provided from (used in) financing activities	61.7	(230.5)	107.7
NET CHANGE IN CASH AND CASH EQUIVALENTS	0	0	0
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	0	0	0
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 0	$ 0	$ 0

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS
Accounts receivable, less reserve of $1.5 and $1.7, respectively	$ 153.8		$ 172.9
Accrued unbilled revenues	64.7		62.6
Advances to parent	304.8		319.5
Fuel inventories	46.3		57.6
Materials and supplies, at average cost	90.6		126.7
Fuel clause under recoveries	39.5		2
Other	19.6		25.5
Total current assets	719.3		766.8
OTHER PROPERTY AND INVESTMENTS	4.7		5
PROPERTY, PLANT AND EQUIPMENT
In service	12,765		11,988.7
Construction work in progress	141.6		376.4
Total property, plant and equipment	12,906.6		12,365.1
Less: accumulated depreciation	3,868.1		3,727.4
Net property, plant and equipment	9,038.5		8,637.7
DEFERRED CHARGES AND OTHER ASSETS
Regulatory assets	306		285.8
Other	8.1		9.2
Total deferred charges and other assets	314.1		295
TOTAL ASSETS	10,076.6		9,704.5
CURRENT LIABILITIES
Accounts payable	175		215
Customer deposits	83		83.6
Accrued taxes	41.9		44
Accrued interest	37.9		44.5
Accrued compensation	29.5		33.8
Long-term debt due within one year	0		250
Fuel clause over recoveries	4.8		0.3
Other	65.1		86.8
Total current liabilities	437.2		758
LONG-TERM DEBT	3,195.2		2,896.9
DEFERRED CREDITS AND OTHER LIABILITIES
Accrued benefit obligations	133.3		137.9
Deferred income taxes	951.4		892.7
Regulatory liabilities	1,223.5		1,270.7
Other	170.6		137.8
Total deferred credits and other liabilities	2,485.9		2,446.3
Total liabilities	6,118.3		6,101.2
COMMITMENTS AND CONTINGENCIES (NOTE 14)
STOCKHOLDER'S EQUITY
Common stockholder's equity	1,036.6		1,031.8
Retained earnings	2,921.7		2,571.5
Total stockholder's equity	3,958.3		3,603.3
TOTAL LIABILITIES AND STOCKHOLDER'S EQUITY	10,076.6		9,704.5
Accumulated Deferred Investment Tax Credit	$ 7.1		$ 7.2

BALANCE SHEETS Parenthetical

BALANCE SHEETS Parenthetical - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable reserve	$ 1.5	$ 1.7

STATEMENTS OF CAPITALIZATION

STATEMENTS OF CAPITALIZATION - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Stockholder's Equity [Abstract]
Common stock, par value $2.50 per share; authorized 100.0 shares; and outstanding 40.4 shares and 40.4 shares, respectively	$ 100.9	$ 100.9
Premium on common stock	935.7	930.9
Retained earnings	2,921.7	2,571.5
Total stockholder's equity	$ 3,958.3	3,603.3
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Total long-term debt	$ 3,195.2	3,146.9
Less: long-term debt due within one year	0	(250)
Total long-term debt (excluding long-term debt due within one year)	3,195.2	2,896.9
Total capitalization (including long-term debt due within one year)	7,153.5	6,750.2
OG&E [Member]
Stockholder's Equity [Abstract]
Unamortized debt expense	(24.2)	(22.9)
Unamortized discount	$ (10.5)	(10.2)
OG&E [Member] | Series Due January 15, 2019 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	8.25%
Long term debt, gross	$ 0	250
OG&E [Member] | Series Due July 15, 2027 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.65%
Long term debt, gross	$ 125	125
OG&E [Member] | Series Due April 15, 2028 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Long term debt, gross	$ 100	100
OG&E [Member] | Series Due August 15, 2028 [Member] [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Long term debt, gross	$ 400	400
OG&E [Member] | Series Due January 15, 2036 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Long term debt, gross	$ 110	110
OG&E [Member] | Series Due February 1, 2038 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Long term debt, gross	$ 200	200
OG&E [Member] | Series Due June 1, 2040 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.85%
Long term debt, gross	$ 250	250
OG&E [Member] | Senior Notes due May 15, 2041 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	5.25%
Long term debt, gross	$ 250	250
OG&E [Member] | Series due May 1, 2043 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.90%
Long term debt, gross	$ 250	250
OG&E [Member] | Series due March 15, 2044 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.55%
Long term debt, gross	$ 250	250
OG&E [Member] | Series due December 15, 2044 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Long term debt, gross	$ 250	250
OG&E [Member] | Due August 31, 2062 [Member] | Long-term Debt [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Long term debt, gross	$ 9.5	9.6
OG&E [Member] | Series due April 1, 2047 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.15%
Long term debt, gross	$ 300	300
OG&E [Member] | Series due August 15, 2047 [Member] [Domain] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Long term debt, gross	$ 300	300
OG&E [Member] | Series Due March 15, 2030 [Member] | Senior Notes [Member]
Stockholder's Equity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Long term debt, gross	$ 300	0
Debentures Subject to Mandatory Redemption [Member]
Stockholder's Equity [Abstract]
Total long-term debt	135.4
Debentures Subject to Mandatory Redemption [Member] | OG&E [Member] | Garfield Industrial Authority Bond, Due January 1, 2025 [Member]
Stockholder's Equity [Abstract]
Long term debt, gross	47	47
Debentures Subject to Mandatory Redemption [Member] | OG&E [Member] | Muskogee Industrial Authority Bond, Due January 1, 2025 [Member]
Stockholder's Equity [Abstract]
Long term debt, gross	32.4	32.4
Debentures Subject to Mandatory Redemption [Member] | OG&E [Member] | Muskogee Industrial Authority Bond, Due June 1, 2027 [Member]
Stockholder's Equity [Abstract]
Long term debt, gross	$ 56	$ 56

STATEMENTS OF CAPITALIZATION (P

STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Common Stock, Par or Stated Value Per Share	$ 2.50	$ 2.50
Common Stock, Shares Authorized	100	100
Common Stock, Shares, Outstanding	40.4	40.4
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Debt Instrument, Maturity Date	Mar. 15, 2030
Garfield Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument, Maturity Date	Jan. 1, 2025
Muskogee Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument, Maturity Date	Jan. 1, 2025
Muskogee Industrial Authority Bond, Due June 1, 2027 [Member]
Debt Instrument, Maturity Date	Jun. 1, 2027
Senior Notes [Member] | OG&E [Member] | Series Due January 15, 2019 [Member]
Debt Instrument, Interest Rate, Stated Percentage	8.25%
Debt Instrument, Maturity Date	Jan. 15, 2019
Senior Notes [Member] | OG&E [Member] | Series Due July 15, 2027 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.65%
Debt Instrument, Maturity Date	Jul. 15, 2027
Senior Notes [Member] | OG&E [Member] | Series Due April 15, 2028 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Debt Instrument, Maturity Date	Apr. 15, 2028
Senior Notes [Member] | OG&E [Member] | Series due August 15, 2028 [Member]
Debt Instrument, Maturity Date	Aug. 15, 2028
Senior Notes [Member] | OG&E [Member] | Series Due January 15, 2036 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Debt Instrument, Maturity Date	Jan. 15, 2036
Senior Notes [Member] | OG&E [Member] | Series Due February 1, 2038 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Debt Instrument, Maturity Date	Feb. 1, 2038
Senior Notes [Member] | OG&E [Member] | Series Due June 1, 2040 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.85%
Debt Instrument, Maturity Date	Jun. 1, 2040
Senior Notes [Member] | OG&E [Member] | Senior Notes due May 15, 2041 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.25%
Debt Instrument, Maturity Date	May 15, 2041
Senior Notes [Member] | OG&E [Member] | Series due May 1, 2043 [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.90%
Debt Instrument, Maturity Date	May 1, 2043
Senior Notes [Member] | OG&E [Member] | Series due March 15, 2044 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.55%
Debt Instrument, Maturity Date	Mar. 15, 2044
Senior Notes [Member] | OG&E [Member] | Series due December 15, 2044 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Debt Instrument, Maturity Date	Dec. 15, 2044
Senior Notes [Member] | OG&E [Member] | Series due April 1, 2047 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.15%
Debt Instrument, Maturity Date	Apr. 1, 2047
Senior Notes [Member] | OG&E [Member] | Series due August 15, 2047 [Member] [Domain]
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Debt Instrument, Maturity Date	Aug. 15, 2047
Long-term Debt [Member] | OG&E [Member] | Due August 31, 2062 [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Debt Instrument, Maturity Date	Aug. 31, 2062
Minimum [Member] | Garfield Industrial Authority Bond, Due January 1, 2025 [Member] | Debentures Subject to Mandatory Redemption [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Minimum [Member] | Muskogee Industrial Authority Bond, Due January 1, 2025 [Member] | Debentures Subject to Mandatory Redemption [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.19%
Minimum [Member] | Muskogee Industrial Authority Bond, Due June 1, 2027 [Member] | Debentures Subject to Mandatory Redemption [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Maximum [Member] | Garfield Industrial Authority Bond, Due January 1, 2025 [Member] | Debentures Subject to Mandatory Redemption [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.50%
Maximum [Member] | Muskogee Industrial Authority Bond, Due January 1, 2025 [Member] | Debentures Subject to Mandatory Redemption [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.35%
Maximum [Member] | Muskogee Industrial Authority Bond, Due June 1, 2027 [Member] | Debentures Subject to Mandatory Redemption [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.48%

STATEMENTS OF CHANGES IN STOCKH

STATEMENTS OF CHANGES IN STOCKHOLDER'S EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Premium on Common Stock	Retained Earnings
Balance, shares		40.4
Dividends declared on common stock, shares		0
Net income, shares		0
Balance at Dec. 31, 2016	$ 3,252.1	$ 100.9	$ 923.2	$ 2,228
Comprehensive income (loss)
Net income	305.5	0	0	305.5
Dividends declared on common stock	(105)	$ 0	0	(105)
Stock-based compensation, shares		0
Stock-based compensation	3.1	$ 0	3.1	0
Balance at Dec. 31, 2017	3,455.7	$ 100.9	926.3	2,428.5
Balance, shares		40.4
Dividends declared on common stock, shares		0
Net income, shares		0
Comprehensive income (loss)
Net income	328	$ 0	0	328
Dividends declared on common stock	(185)	$ 0	0	(185)
Stock-based compensation, shares		0
Stock-based compensation	4.6	$ 0	4.6	0
Balance at Dec. 31, 2018	$ 3,603.3	$ 100.9	930.9	2,571.5
Balance, shares	40.4	40.4
Net income, shares		0
Comprehensive income (loss)
Net income	$ 350.2	$ 0	0	350.2
Dividends declared on common stock				0
Stock-based compensation, shares		0
Stock-based compensation	4.8	$ 0	4.8	0
Balance at Dec. 31, 2019	$ 3,958.3	$ 100.9	$ 935.7	$ 2,921.7
Balance, shares	40.4	40.4

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Cash Flow, Supplemental Disclosures [Text Block]	Supplemental Cash Flow Information The following table presents information about investing and financing activities that affected recognized assets and liabilities but did not result in cash receipts or payments. Cash paid for interest, net of interest capitalized, and cash paid for income taxes, net of income tax refunds are also presented in the table. Year Ended December 31 (In millions) 2019 2018 2017 NON-CASH INVESTING AND FINANCING ACTIVITIES Power plant long-term service agreement $ 28.9 $ (9.2) $ (2.6) SUPPLEMENTAL CASH FLOW INFORMATION Cash paid during the period for: Interest (net of interest capitalized) (A) $ 144.6 $ 149.7 $ 133.1 Income taxes (net of income tax refunds) $ 1.3 $ 0.9 $ (71.5)

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	The following table presents information about investing and financing activities that affected recognized assets and liabilities but did not result in cash receipts or payments. Cash paid for interest, net of interest capitalized, and cash paid for income taxes, net of income tax refunds are also presented in the table. Year Ended December 31 (In millions) 2019 2018 2017 NON-CASH INVESTING AND FINANCING ACTIVITIES Power plant long-term service agreement $ 28.9 $ (9.2) $ (2.6) SUPPLEMENTAL CASH FLOW INFORMATION Cash paid during the period for: Interest (net of interest capitalized) (A) $ 144.6 $ 149.7 $ 133.1 Income taxes (net of income tax refunds) $ 1.3 $ 0.9 $ (71.5)

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
NON-CASH INVESTING AND FINANCING ACTIVITIES
Power plant long-term service agreement		$ 28.9	$ (9.2)	$ (2.6)
SUPPLEMENTAL CASH FLOW INFORMATION
Interest (net of interest capitalized)	[1]	144.6	149.7	133.1
Income taxes (net of income tax refunds)		1.3	0.9	(71.5)
Interest costs capitalized		$ 2.8	$ 11.7	$ 18
[1]	Net of interest capitalized of $2.8 million, $11.7 million and $18.0 million in 2019, 2018 and 2017, respectively.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Regulatory Assets and Liabilities [Text Block]	Accounting Records The accounting records of OG&E are maintained in accordance with the Uniform System of Accounts prescribed by the FERC and adopted by the OCC and the APSC. Additionally, OG&E, as a regulated utility, is subject to accounting principles for certain types of rate-regulated activities, which provide that certain incurred costs that would otherwise be charged to expense can be deferred as regulatory assets, based on the expected recovery from customers in future rates. Likewise, certain actual or anticipated credits that would otherwise reduce expense can be deferred as regulatory liabilities, based on the expected flowback to customers in future rates. Management's expected recovery of deferred costs and flowback of deferred credits generally results from specific decisions by regulators granting such ratemaking treatment. OG&E records certain incurred costs and obligations as regulatory assets or liabilities if, based on regulatory orders or other available evidence, it is probable that the costs or obligations will be included in amounts allowable for recovery or refund in future rates. The following table is a summary of OG&E's regulatory assets and liabilities. December 31 (In millions) 2019 2018 REGULATORY ASSETS Current: Fuel clause under recoveries $ 39.5 $ 2.0 Production tax credit rider over credit (A) 1.7 6.9 Oklahoma demand program rider under recovery (A) — 6.4 Other (A) 7.5 3.2 Total current regulatory assets $ 48.7 $ 18.5 Non-current: Benefit obligations regulatory asset $ 167.2 $ 188.2 Deferred storm expenses 65.5 36.5 Sooner Dry Scrubbers 20.6 4.5 Smart Grid 18.4 25.6 Unamortized loss on reacquired debt 10.6 11.4 Arkansas deferred pension expenses 8.0 6.8 Pension tracker 2.3 — Other 13.4 12.8 Total non-current regulatory assets $ 306.0 $ 285.8 REGULATORY LIABILITIES Current: Reserve for tax refund and interim surcharge (B) $ 12.7 $ 15.4 Fuel clause over recoveries 4.8 0.3 SPP cost tracker over recovery (B) 2.6 16.8 Oklahoma demand program rider over recovery (B) 2.0 — Transmission cost recovery rider over recovery (B) — 2.7 Other (B) 6.9 1.4 Total current regulatory liabilities $ 29.0 $ 36.6 Non-current: Income taxes refundable to customers, net $ 899.2 $ 937.1 Accrued removal obligations, net 318.5 308.1 Pension tracker — 18.7 Other 5.8 6.8 Total non-current regulatory liabilities $ 1,223.5 $ 1,270.7 (A) Included in Other Current Assets in the Balance Sheets. (B) Included in Other Current Liabilities in the Balance Sheets. Fuel clause under and over recoveries are generated from OG&E's customers when OG&E's cost of fuel either exceeds or is less than the amount billed to its customers, respectively. OG&E's fuel recovery clauses are designed to smooth the impact of fuel price volatility on customers' bills. As a result, OG&E under recovers fuel costs in periods of rising fuel prices above the baseline charge for fuel and over recovers fuel costs when prices decline below the baseline charge for fuel. Provisions in the fuel clauses are intended to allow OG&E to amortize under and over recovery balances. As approved by the OCC, OG&E utilizes a rider separate from base rates to credit customers for production tax credits. OG&E recovers program costs related to the Demand and Energy Efficiency Program in Oklahoma through the Demand Program Rider, which operates on a three-year program cycle. The current program cycle, which runs through 2021, includes recovery of (i) energy efficiency program costs, (ii) lost revenues associated with certain achieved energy efficiency and demand savings, (iii) performance-based incentives and (iv) costs associated with research and development investments. The benefit obligations regulatory asset is comprised of expenses recorded which are probable of future recovery and that have not yet been recognized as components of net periodic benefit cost, including net loss and prior service cost. These expenses are recorded as a regulatory asset as OG&E historically has recovered and currently recovers pension and postretirement benefit plan expense in its electric rates. If, in the future, the regulatory bodies indicate a change in policy related to the recovery of pension and postretirement benefit plan expenses, this could cause the benefit obligations regulatory asset balance to be reclassified to accumulated other comprehensive income. The following table is a summary of the components of the benefit obligations regulatory asset: December 31 (In millions) 2019 2018 Pension Plan and Restoration of Retirement Income Plan: Net loss $ 160.5 $ 185.3 Postretirement Benefit Plans: Net loss 23.3 25.6 Prior service cost (16.6) (22.7) Total $ 167.2 $ 188.2 The following amounts in the benefit obligations regulatory asset at December 31, 2019 are expected to be recognized as components of net periodic benefit cost in 2020: (In millions) Pension Plan and Restoration of Retirement Income Plan: Net loss $ 11.4 Postretirement Benefit Plans: Net loss 2.8 Prior service cost (6.1) Total $ 8.1 OG&E includes in expense any Oklahoma storm-related operation and maintenance expenses up to $2.7 million annually and defers to a regulatory asset any additional expenses incurred over $2.7 million. OG&E expects to recover the amounts deferred each year over a five-year period in accordance with historical practice. As approved by the OCC in June 2018, OG&E deferred the non-fuel incremental operation and maintenance expenses, depreciation, debt cost associated with the capital investment and related ad valorem taxes for the Dry Scrubbers at Sooner Units 1 and 2 as a regulatory asset. As approved by the OCC, these costs are being recovered over 25 years. OG&E deferred to a regulatory asset the incremental and stranded costs that were accumulated during Smart Grid deployment, including (i) costs for web portal access, (ii) costs for education and home energy reports and (iii) stranded costs associated with OG&E's analog electric meters, which have been replaced by smart meters. As approved by the OCC and APSC, these costs are being recovered over a six-year period. Unamortized loss on reacquired debt is comprised of unamortized debt issuance costs related to the early retirement of OG&E's long-term debt. These amounts are recorded in interest expense and are being amortized over the term of the long-term debt which replaced the previous long-term debt. The unamortized loss on reacquired debt is recovered as a part of OG&E's cost of capital. Arkansas includes a certain level of pension expense in base rates. When the Pension Plan experiences a settlement, which represents an acceleration of future pension costs, OG&E defers to a regulatory asset the Arkansas jurisdictional portion of each settlement, which historically was recovered from customers over the average life of the remaining plan participants. A portion of these settlements is being recovered in current rates, and recovery of additional amounts will be requested as additional settlements occur. For additional information related to settlements, see Note 13. OG&E recovers specific amounts of pension and postretirement medical costs in rates approved in its Oklahoma rate reviews. In accordance with approved orders, OG&E defers the difference between actual pension and postretirement medical expenses and the amount approved in its last Oklahoma rate review as a regulatory asset or regulatory liability. These amounts have been recorded in the Pension tracker regulatory asset in the table above. As a result of 2018 filings with the OCC, APSC and FERC, OG&E established mechanisms to refund to customers the amount of excess taxes received through rates, with an ongoing adjustment for any excess accumulated deferred income taxes resulting from the 2017 Tax Act. Additional amounts due to customers will be refunded in accordance with agreements in each jurisdiction. OG&E recovers certain SPP costs related to base plan charges from its customers and refunds certain SPP revenues received to its customers in Oklahoma through the SPP cost tracker and in Arkansas through the transmission cost recovery rider. Income taxes refundable to customers, net, represents the reduction in accumulated deferred income taxes resulting from the reduction in the federal income tax rate as part of the 2017 Tax Act and includes income taxes recoverable from customers that represent income tax benefits previously used to reduce OG&E's revenues (treated as regulatory assets). These liabilities will be returned to customers in varying amounts over approximately 80 years, and the assets will be amortized over the estimated remaining life of the assets to which they relate, as the temporary differences that generated the income tax benefits turn around. Accrued removal obligations, net represents asset retirement costs previously recovered from ratepayers for other than legal obligations.
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Summary of Significant Accounting Policies Organization OG&E generates, transmits, distributes and sells electric energy in Oklahoma and western Arkansas. Its operations are subject to regulation by the OCC, the APSC and the FERC. OG&E was incorporated in 1902 under the laws of the Oklahoma Territory. OG&E is the largest electric utility in Oklahoma, and its franchised service territory includes Fort Smith, Arkansas and the surrounding communities. OG&E sold its retail natural gas business in 1928 and is no longer engaged in the natural gas distribution business. OG&E is a wholly-owned subsidiary of OGE Energy, a holding company with investments in energy and energy services providers offering physical delivery and related services for both electricity and natural gas primarily in the south central U.S. Cash and Cash Equivalents Allowance for Uncollectible Accounts Receivable Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off. To the extent the historical collection rates are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the Balance Sheets and is included in Other Operation and Maintenance Expense in the Statements of Income. The allowance for uncollectible accounts receivable was $1.5 million and $1.7 million at December 31, 2019 and 2018, respectively. New business customers are required to provide a security deposit in the form of cash, bond or irrevocable letter of credit that is refunded when the account is closed. New residential customers whose outside credit scores indicate an elevated risk are required to provide a security deposit that is refunded based on customer protection rules defined by the OCC and the Depreciation and Amortization The provision for depreciation, which was 2.7 percent of the average depreciable utility plant for both 2019 and 2018, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2020, the provision for depreciation is projected to be 2.7 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2019, 98.9 percent will be amortized over 10.4 years with the remaining 1.1 percent of the intangible plant balance at December 31, 2019 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life and $3.3 million for certain transmission substation facilities in OG&E's service territory, which are being amortized over a 37 to 59 year period. Allowance for Funds Used During Construction Allowance for funds used during construction, a non-cash item, is reflected as an increase to Net Other Income and a reduction to Interest Expense in the Statements of Income and as an increase to Construction Work in Progress in the Balance Sheets. Allowance for funds used during construction is calculated according to the FERC requirements for the imputed cost of equity and borrowed funds. Allowance for funds used during construction rates, compounded semi-annually, were 7.6 percent, 7.6 percent and 8.2 percent for the years ended December 31, 2019, 2018 and 2017, respectively. Collection of Sales Tax In the normal course of its operations, OG&E collects sales tax from its customers. OG&E records a current liability for sales taxes when it bills its customers and eliminates this liability when the taxes are remitted to the appropriate governmental authorities. OG&E excludes the sales tax collected from its operating revenues. Revenue Recognition General OG&E recognizes revenue from electric sales when power is delivered to customers. The performance obligation to deliver electricity is generally created and satisfied simultaneously, and the provisions of the regulatory-approved tariff determine the charges OG&E may bill the customer, payment due date and other pertinent rights and obligations of both parties. OG&E reads its customers' meters and sends bills to its customers throughout each month. As a result, there is a significant amount of customers' electricity consumption that has not been billed at the end of each month. OG&E accrues an estimate of the revenues for electric sales delivered since the latest billings. Unbilled revenue is presented in Accrued Unbilled Revenues in the Balance Sheets and in Revenues from Contracts with Customers in the Statements of Income based on estimates of usage and prices during the period. The estimates that management uses in this calculation could vary from the actual amounts to be paid by customers. Integrated Market and Transmission OG&E currently owns and operates transmission and generation facilities as part of a vertically integrated utility. OG&E is a member of the SPP regional transmission organization and has transferred operational authority, but not ownership, of OG&E's transmission facilities to the SPP. The SPP has implemented FERC-approved regional day-ahead and real-time markets for energy and operating services, as well as associated transmission congestion rights. Collectively the three markets operate together under the global name, SPP Integrated Marketplace. OG&E represents owned and contracted generation assets and customer load in the SPP Integrated Marketplace for the sole benefit of its customers. OG&E has not participated in the SPP Integrated Marketplace for any speculative trading activities. OG&E records the SPP Integrated Marketplace transactions as sales or purchases per FERC Order 668, which requires that purchases and sales be recorded on a net basis for each settlement period of the SPP Integrated Marketplace. Purchases and sales are based on the fixed transaction price determined by the market at the time of the purchase or sale and the MWh quantity purchased or sold. These results are reported as Revenues from Contracts with Customers or Cost of Sales in the Financial Statements. OG&E revenues, expenses, assets and liabilities may be adversely affected by changes in the organization, operating and regulation by the FERC or the SPP. OG&E's transmission revenues are generated by the use of OG&E's transmission network by the SPP, which operates the network, on behalf of other transmission owners. OG&E recognizes revenue on the sale of transmission service to its customers over time as the service is provided in the amount OG&E has a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by OG&E's FERC-approved formula transmission rates along with other SPP-specific charges and the megawatt quantity reserved. Other Revenues Revenues from Alternative Revenue Programs Other Revenues in the Statements of Income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either program type have been completed, OG&E recognizes the additional revenues if (i) the program is established by an order from OG&E's regulatory commission that allows for automatic adjustment of future rates; (ii) the amount of additional revenues for the period is objectively determinable and is probable of recovery; and (iii) the additional revenues will be collected within 24 months following the end of the annual period in which they are recognized. Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC. Leases OG&E evaluates all contracts under ASC 842 to determine if the contract is or contains a lease and to determine classification as an operating or finance lease. If a lease is identified, OG&E recognizes a right-of-use asset and a lease liability in its Balance Sheets. OG&E recognizes and measures a lease liability when it concludes the contract contains an identified asset that OG&E controls through having the right to obtain substantially all of the economic benefits and the right to direct the use of the identified asset. The liability is equal to the present value of lease payments, and the asset is based on the liability, subject to adjustment, such as for initial direct costs. Further, OG&E utilizes an incremental borrowing rate for purposes of measuring lease liabilities, if the discount rate is not implicit in the lease. To calculate the incremental borrowing rate, OG&E starts with a current pricing report for OG&E's senior unsecured notes, which indicates rates for periods reflective of the lease term, and adjusts for the effects of collateral to arrive at the secured incremental borrowing rate. As permitted by ASC 842, OG&E made an accounting policy election to not apply the balance sheet recognition requirements to short-term leases and to not separate lease components from nonlease components when recognizing and measuring lease liabilities. For income statement purposes, OG&E records operating lease expense on a straight-line basis. Accrued Vacation OG&E accrues vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.
Inventory Disclosure [Text Block]	Fuel Inventories Fuel inventories for the generation of electricity consist of coal, natural gas and oil. OG&E uses the weighted-average cost method of accounting for inventory that is physically added to or withdrawn from storage or stockpiles. The amount of fuel inventory was $46.3 million and $57.6 million at December 31, 2019 and 2018, respectively.
Property, Plant and Equipment Disclosure [Text Block]	Property, Plant and Equipment All property, plant and equipment is recorded at cost. Newly constructed plant is added to plant balances at cost which includes contracted services, direct labor, materials, overhead, transportation costs and the allowance for funds used during construction. Replacements of units of property are capitalized as plant. For assets that belong to a common plant account, the replaced plant is removed from plant balances, and the cost of such property net of any salvage proceeds is charged to Accumulated Depreciation. For assets that do not belong to a common plant account, the replaced plant is removed from plant balances with the related accumulated depreciation, and the remaining balance net of any salvage proceeds is recorded as a loss in the Statements of Income as Other Expense. Repair and replacement of minor items of property are included in the Statements of Income as Other Operation and Maintenance Expense. The tables below 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, 2019 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 254.4 $ 83.5 $ 170.9 Redbud Plant (A)(B) 51 % $ 529.9 $ 159.0 $ 370.9 (A) Construction work in progress was $0.2 million and $1.4 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. December 31, 2018 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 227.2 $ 78.2 $ 149.0 Redbud Plant (A)(B) 51 % $ 493.9 $ 145.3 $ 348.6 (A) Construction work in progress was $0.2 million and $0.9 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $56.3 million. OG&E's property, plant and equipment and related accumulated depreciation are divided into the following major classes: December 31, 2019 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment Distribution assets $ 4,468.6 $ 1,381.1 $ 3,087.5 Electric generation assets (A) 4,838.6 1,601.0 3,237.6 Transmission assets (B) 2,901.1 565.5 2,335.6 Intangible plant 225.2 145.4 79.8 Other property and equipment 473.1 175.1 298.0 Total property, plant and equipment $ 12,906.6 $ 3,868.1 $ 9,038.5 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.8 million. December 31, 2018 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment Distribution assets $ 4,229.4 $ 1,324.5 $ 2,904.9 Electric generation assets (A) 4,657.2 1,572.8 3,084.4 Transmission assets (B) 2,846.7 534.2 2,312.5 Intangible plant 187.6 135.1 52.5 Other property and equipment 444.2 160.8 283.4 Total property, plant and equipment $ 12,365.1 $ 3,727.4 $ 8,637.7 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $56.3 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.7 million. OG&E's unamortized computer software costs, included in intangible plant above, were $71.3 million and $44.3 million at December 31, 2019 and 2018, respectively. In 2019, 2018 and 2017, amortization expense for computer software costs was $11.0 million, $9.6 million and $8.8 million, respectively.
Asset Retirement Obligation Disclosure [Text Block]	Asset Retirement Obligations OG&E has asset retirement obligations primarily associated with the removal of company-owned wind turbines on leased land, as well as the removal of asbestos from certain power generating stations. OG&E has recorded asset retirement obligations that are being accreted over their respective lives ranging from ten to 68 years. The following table summarizes changes to OG&E's asset retirement obligations during the years ended December 31, 2019 and 2018. (In millions) 2019 2018 Balance at January 1 $ 83.9 $ 75.1 Accretion expense 1.0 3.4 Revisions in estimated cash flows (A) (2.4) 6.8 Liabilities settled (B) (9.0) (1.4) Balance at December 31 $ 73.5 $ 83.9 (A) Assumptions changed related to the estimated cost of the removal of wind turbine assets and asbestos removal at OG&E's generating facilities. (B) Asset retirement obligations were settled for asbestos removal and for the closure of an ash pond at OG&E's generating facilities.
Reclassifications [Text Block]	ReclassificationsCertain prior year amounts have been reclassified to conform to the current year presentation.

Accounting Pronouncement

Accounting Pronouncement	12 Months Ended
	Dec. 31, 2019
Accounting Pronouncement [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Accounting Pronouncements Recently Adopted Accounting Standards Leases. In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)." The main difference between prior lease accounting and ASC 842 is the recognition of right-of-use assets and lease liabilities by lessees for those leases classified as operating leases under current accounting guidance. Lessees, such as OG&E, recognize a right-of-use asset and a lease liability for virtually all of their leases, other than leases that meet the definition of a short-term lease. The liability is equal to the present value of lease payments. The asset is based on the liability, subject to adjustment for items such as initial direct costs. For income statement purposes, ASC 842 retains a dual model, requiring leases to be classified as either operating or finance. Operating leases result in straight-line expense, while finance leases result in a front-loaded expense pattern, similar to prior capital leases. Classification of operating and finance leases is based on criteria that are largely similar to those applied in prior lease guidance but without the explicit thresholds. OG&E adopted this standard in the first quarter of 2019 utilizing the modified retrospective transition method. Various practical expedients for the application of ASC 842 were approved, and OG&E elected to apply the below: • a package of practical expedients allowing entities to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) the lease classification for any expired or existing leases and (iii) initial direct costs for any existing leases; • an option that permits an entity to elect a transitional practical expedient, to be applied consistently, to not evaluate under ASC 842 land easements that exist or expired before the entity's adoption of ASC 842 and that were not previously accounted for as leases under ASC 840, "Leases"; and • an option that permits an entity to elect to initially apply ASC 842 at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption, provided that if an entity elects this additional (and optional) transition method, the entity will provide the required ASC 840 disclosures for all periods that continue to be reported under ASC 840. OG&E evaluated its current lease contracts and, at January 1, 2019, recognized $32.3 million and $36.9 million of operating lease right-of-use assets and liabilities, respectively, for railcar, wind farm land and office space leases in the Balance Sheet. The new standard did not have a material impact on OG&E's 2019 Statement of Income. Further, OG&E evaluated its existing processes and controls regarding lease identification, accounting and presentation and implemented changes as necessary in order to adequately address the requirements of ASC 842. Financial Instruments-Credit Losses. In June 2016, the FASB issued ASU No. 2016-13, "Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Information." The amendments in this update require entities to measure all expected credit losses of financial assets held at a reporting date based on historical experience, current conditions and reasonable and supportable forecasts in order to record credit losses in a more timely manner. ASU 2016-13 also amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 is effective for fiscal years beginning after December 2019 and is applied utilizing a modified-retrospective approach. OG&E determined the only financial instrument that OG&E currently holds and is required to measure under ASU 2016-13 is its trade receivables. Upon adoption of this ASU, OG&E considers forecasts of future economic conditions in addition to the historical data utilized prior to ASU 2016-13 when measuring the reserve for trade receivables. OG&E evaluated its reserve for trade receivables in light of the new guidance and determined that no adjustment was necessary to the amount recorded as of January 1, 2020. Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The new guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 is effective for fiscal years beginning after December 2019 and can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. OG&E adopted and prospectively applied the new guidance beginning in the first quarter of 2020, which did not have a material effect on the Financial Statements upon adoption. Issued Accounting Standards Not Yet Adopted Simplifying the Accounting for Income Taxes. In December 2019, the FASB issued ASU 2019-12, "Income Taxes (Topic 740)." The new guidance simplifies the accounting for income taxes by removing certain exceptions to the general

Revenue Recognition (Notes)

Revenue Recognition (Notes)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	Revenue Recognition The following table disaggregates OG&E's revenues from contracts with customers by customer classification. OG&E's operating revenues disaggregated by customer classification can be found in "OG&E (Electric Utility) Results of Operations" within "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations." Year Ended December 31, (In millions) 2019 2018 Residential $ 865.8 $ 877.8 Commercial 486.6 500.0 Industrial 217.8 228.9 Oilfield 200.4 190.4 Public authorities and street light 190.3 197.4 System sales revenues 1,960.9 1,994.5 Provision for rate refund (0.9) (6.0) Integrated market 38.4 48.7 Transmission 148.0 147.4 Other 29.1 27.1 Revenues from contracts with customers $ 2,175.5 $ 2,211.7

Related-Party Transactions Rela

Related-Party Transactions Related-Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transaction [Line Items]
Related Party Transactions Disclosure [Text Block]	Related Party Transactions OGE Energy charged operating costs to OG&E of $149.8 million, $140.9 million and $134.4 million in 2019, 2018 and 2017, respectively. OGE Energy charges operating costs to OG&E based on several factors. Operating costs directly related to OG&E are assigned as such. Operating costs incurred for the benefit of OG&E are allocated either as overhead based primarily on labor costs or using the "Distrigas" method. In 2019, no dividends were declared from OG&E to OGE Energy, compared to $185.0 million and $105.0 million in 2018 and 2017, respectively. Enable provides gas transportation services to OG&E pursuant to an agreement, which expires in May 2024, that grants Enable the responsibility of delivering natural gas to OG&E's generating facilities and performing an imbalance service. With this imbalance service, in accordance with the cash-out provision of the contract, OG&E purchases gas from Enable when Enable's deliveries exceed OG&E's pipeline receipts. Enable purchases gas from OG&E when OG&E's pipeline receipts exceed Enable's deliveries. Further, an additional gas transportation services contract with Enable became effective in December 2018 related to the project to convert Muskogee Units 4 and 5 from coal to natural gas. The following table summarizes related party transactions between OG&E and Enable during the years ended December 31, 2019, 2018 and 2017. Year Ended December 31, (In millions) 2019 2018 2017 Operating revenues: Electricity to power electric compression assets $ 15.9 $ 16.3 $ 14.0 Cost of sales: Natural gas transportation services $ 41.2 $ 37.9 $ 35.0 Natural gas (sales) purchases $ (6.0) $ (3.2) $ (2.1)

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The classification of OG&E's fair value measurements requires judgment regarding the degree to which market data is observable or corroborated by observable market data. GAAP establishes a fair value hierarchy that prioritizes the inputs used to measure fair value based on observable and unobservable data. The hierarchy categorizes the inputs into three levels, with the highest priority given to quoted prices in active markets for identical unrestricted assets or liabilities (Level 1) and the lowest priority given to unobservable inputs (Level 3). Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels defined in the fair value hierarchy are as follows: Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the reporting entity's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). OG&E had no financial instruments measured at fair value on a recurring basis at December 31, 2019 and 2018. The following table summarizes the carrying amount and fair value of OG&E's financial instruments at December 31, 2019 and 2018, as well as the classification level within the fair value hierarchy. 2019 2018 December 31 (In millions) Carrying Fair Carrying Fair Classification Long-term Debt (including Long-term Debt due within one year): Senior Notes $ 3,050.3 $ 3,500.4 $ 3,001.9 $ 3,178.2 Level 2 Industrial Authority Bonds $ 135.4 $ 135.4 $ 135.4 $ 135.4 Level 2 Tinker Debt $ 9.5 $ 10.0 $ 9.6 $ 8.7 Level 3

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	Stock-Based Compensation In 2013, OGE Energy adopted, and its shareholders approved, the Stock Incentive Plan. Under the Stock Incentive Plan, restricted stock, restricted stock units, stock options, stock appreciation rights and performance units may be granted to officers, directors and other key employees of OGE Energy and its subsidiaries. OGE Energy has authorized the issuance of up to 7,400,000 shares under the Stock Incentive Plan. The following table summarizes OG&E's pre-tax compensation expense and related income tax benefit for the years ended December 31, 2019, 2018 and 2017 related to performance units and restricted stock units for OG&E employees. Year Ended December 31 (In millions) 2019 2018 2017 Performance units: Total shareholder return $ 3.0 $ 2.8 $ 2.5 Earnings per share 1.5 1.8 0.5 Total performance units 4.5 4.6 3.0 Restricted stock units 0.4 — — Total compensation expense $ 4.9 $ 4.6 $ 3.0 Income tax benefit $ 1.3 $ 1.2 $ 1.2 OGE Energy has issued new shares of common stock to satisfy restricted stock unit grants and payouts of earned performance units. In 2019, 2018 and 2017, there were 164,794 shares, 8,599 shares and 965 shares, respectively, of new common stock issued to OG&E's employees pursuant to OGE Energy's Stock Incentive Plan related to restricted stock unit grants and payouts of earned performance units. Performance Units Under the Stock Incentive Plan, OGE Energy has issued performance units which represent the value of one share of OGE Energy's common stock. The performance units provide for accelerated vesting if there is a change in control (as defined in the Stock Incentive Plan). Each performance unit is subject to forfeiture if the recipient terminates employment with OGE Energy or a subsidiary prior to the end of the primarily three-year award cycle for any reason other than death, disability or retirement. In the event of death, disability or retirement, a participant will receive a prorated payment based on such participant's number of full months of service during the award cycle, further adjusted based on the achievement of the performance goals during the award cycle. OG&E estimates expected forfeitures in accounting for performance unit compensation expense. The performance units granted based on total shareholder return are contingently awarded and will be payable in shares of OGE Energy's common stock subject to the condition that the number of performance units, if any, earned by the employees upon the expiration of a primarily three-year award cycle (i.e., three-year cliff vesting period) is dependent on OGE Energy's total shareholder return ranking relative to a peer group of companies. The performance units granted based on earnings per share are contingently awarded and will be payable in shares of OGE Energy's common stock based on OGE Energy's earnings per share growth over a primarily three-year award cycle (i.e., three-year cliff vesting period) compared to a target set at the time of the grant by the Compensation Committee of OGE Energy's Board of Directors. All of these performance units are classified as equity in OGE Energy's Consolidated Balance Sheets. If there is no or only a partial payout for the performance units at the end of the award cycle, the unearned performance units are cancelled. Payout requires approval of the Compensation Committee of OGE Energy's Board of Directors. Payouts, if any, are all made in common stock and are considered made when the payout is approved by the Compensation Committee. Performance Units – Total Shareholder Return The fair value of the performance units based on total shareholder return was estimated on the grant date using a lattice-based valuation model that factors in information, including the expected dividend yield, expected price volatility, risk-free interest rate and the probable outcome of the market condition, over the expected life of the performance units. Compensation expense for the performance units is a fixed amount determined at the grant date fair value and is recognized over the primarily three-year award cycle regardless of whether performance units are awarded at the end of the award cycle. Dividends are accrued on a quarterly basis pending achievement of payout criteria and are included in the fair value calculations. Expected price volatility is based on the historical volatility of OGE Energy's common stock for the past three years and was simulated using the Geometric Brownian Motion process. The risk-free interest rate for the performance unit grants is based on the three-year U.S. Treasury yield curve in effect at the time of the grant. The expected life of the units is based on the non-vested period since inception of the award cycle. There are no post-vesting restrictions related to OGE Energy's performance units based on total shareholder return. The number of performance units granted based on total shareholder return and the assumptions used to calculate the grant date fair value of the performance units based on total shareholder return are shown in the following table. 2019 2018 2017 Number of units granted to OG&E employees 68,396 91,940 85,501 Fair value of units granted $ 47.00 $ 36.86 $ 41.76 Expected dividend yield 4.0 % 3.6 % 3.8 % Expected price volatility 17.0 % 19.0 % 19.8 % Risk-free interest rate 2.47 % 2.38 % 1.46 % Expected life of units (in years) 2.86 2.86 2.86 Performance Units – Earnings Per Share The fair value of the performance units based on earnings per share is based on grant date fair value which is equivalent to the price of one share of OGE Energy's common stock on the date of grant. The fair value of performance units based on earnings per share varies as the number of performance units that will vest is based on the grant date fair value of the units and the probable outcome of the performance condition. OGE Energy reassesses at each reporting date whether achievement of the performance condition is probable and accrues compensation expense if and when achievement of the performance condition is probable. As a result, the compensation expense recognized for these performance units can vary from period to period. There are no post-vesting restrictions related to OGE Energy's performance units based on earnings per share. In 2019, the Compensation Committee of OGE Energy's Board of Directors voted to grant restricted stock units in lieu of performance units based on earnings per share. For 2018 and 2017, the number of performance units granted based on earnings per share and the grant date fair value are shown in the following table. 2018 2017 Number of units granted to OG&E employees 30,649 28,499 Fair value of units granted $ 31.03 $ 34.83 Restricted Stock Units Under the Stock Incentive Plan, OGE Energy has issued restricted stock units to certain existing non-officer employees as well as other executives upon hire to attract and retain individuals to be competitive in the marketplace, and for the 2019 grant cycle, restricted stock units were granted in lieu of performance units based on earnings per share. The restricted stock units vest primarily in a three-year award cycle (i.e., three-year cliff vesting period). Prior to vesting, each restricted stock unit is subject to forfeiture if the recipient ceases to render substantial services to OGE Energy or a subsidiary. These restricted stock units may not be sold, assigned, transferred or pledged and are subject to a risk of forfeiture. The fair value of the restricted stock units was based on the closing market price of OGE Energy's common stock on the grant date. Compensation expense for the restricted stock units is a fixed amount determined at the grant date fair value and is recognized as services are rendered by employees over a primarily three-year vesting period. Also, for those restricted stock units that vest in one-third annual increments over a three-year cycle, OG&E treats its restricted stock units as multiple separate awards by recording compensation expense separately for each tranche whereby a substantial portion of the expense is recognized in the earlier years in the requisite service period. Dividends will only be paid on restricted stock unit awards that vest; therefore, only the present value of dividends expected to vest are included in the fair value calculations. The expected life of the restricted stock units is based on the non-vested period since inception of the primarily three-year award cycle. There are no post-vesting restrictions related to OGE Energy's restricted stock units. In 2019, 26,141 restricted stock units were granted to OG&E employees at a fair value of $41.63. There were no restricted stock unit grants made to OG&E employees during 2018 or 2017. Performance Units and Restricted Stock Units Activity A summary of the activity for OGE Energy's performance units and restricted stock units applicable to OG&E's employees at December 31, 2019 and changes in 2019 are shown in the following table. Performance Units Restricted Total Shareholder Return Earnings Per Share (Dollars in millions) Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Units/shares outstanding at 12/31/18 261,423 87,143 312 Granted 68,396 (A) — 26,141 Converted (95,593) (B) $ 7.0 (31,865) (B) $ 2.5 N/A Vested N/A N/A (312) $ — Forfeited (10,360) (2,207) (1,500) Employee migration 3,813 (C) 906 (C) 364 (C) Units/shares outstanding at 12/31/19 227,679 $ 12.2 53,977 $ 4.0 25,005 $ 1.1 Units/shares fully vested at 12/31/19 77,799 $ 4.0 25,931 $ 2.3 (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) These amounts represent performance units that vested at December 31, 2018 which were settled in February 2019. (C) Due to certain employees transferring between OG&E and OGE Energy. A summary of the activity for OGE Energy's non-vested performance units and restricted stock units applicable to OG&E's employees at December 31, 2019 and changes in 2019 are shown in the following table. Performance Units Restricted Total Shareholder Return Earnings Per Share Number Weighted-Average Number Weighted-Average Number Weighted-Average Units/shares non-vested at 12/31/18 165,830 $ 39.17 55,278 $ 32.82 312 $ 31.88 Granted 68,396 (A) $ 47.00 — $ — 26,141 $ 41.63 Vested (77,799) $ 41.76 (25,931) $ 34.83 (312) $ 31.88 Forfeited (10,360) $ 41.33 (2,207) $ 32.02 (1,500) $ 41.78 Employee migration 3,813 (B) $ 41.43 906 (B) $ 32.84 364 (B) $ 41.78 Units/shares non-vested at 12/31/19 149,880 $ 41.31 28,046 $ 31.03 25,005 $ 41.62 Units/shares expected to vest 145,790 (C) 28,006 (C) 20,251 (C) (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) Due to certain employees transferring between OG&E and OGE Energy. (C) The intrinsic value of the performance units based on total shareholder return and earnings per share is $8.1 million and $1.7 million, respectively. The intrinsic value of restricted stock units is $0.9 million. Fair Value of Vested Performance Units and Restricted Stock Units A summary of OG&E's fair value for its vested performance units and restricted stock units is shown in the following table. Year Ended December 31 (In millions) 2019 2018 2017 Performance units: Total shareholder return $ 3.2 $ 2.1 $ 2.3 Earnings per share $ 0.9 $ 1.7 $ 0.4 Restricted stock units $ — $ — $ 0.1 Unrecognized Compensation Cost A summary of OG&E's unrecognized compensation cost for its non-vested performance units and restricted stock units and the weighted-average periods over which the compensation cost is expected to be recognized are shown in the following table. December 31, 2019 Unrecognized Compensation Cost (In millions) Weighted Average to be Recognized (In years) Performance units: Total shareholder return $ 3.0 1.68 Earnings per share 0.3 1.00 Total performance units 3.3 Restricted stock units 0.7 2.00 Total unrecognized compensation cost $ 4.0

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax Disclosure Text Block	Income Taxes Income Tax Expense (Benefit) The items comprising income tax expense (benefit) are as follows: Year Ended December 31 (In millions) 2019 2018 2017 Provision (benefit) for current income taxes: Federal $ (7.9) $ (12.4) $ 26.3 State 4.1 (4.1) (4.3) Total provision (benefit) for current income taxes (3.8) (16.5) 22.0 Provision (benefit) for deferred income taxes, net: Federal 37.7 53.7 100.0 State (13.8) 2.7 19.9 Total provision for deferred income taxes, net 23.9 56.4 119.9 Deferred federal investment tax credits, net — 0.1 (0.1) Total income tax expense $ 20.1 $ 40.0 $ 141.8 OG&E is a member of an affiliated group that files consolidated income tax returns in the U.S. federal jurisdiction and various state jurisdictions. With few exceptions, OG&E is no longer subject to U.S. federal tax or state and local examinations by tax authorities for years prior to 2016. Income taxes are generally allocated to each company in the affiliated group based on its stand-alone taxable income or loss. Federal investment tax credits previously claimed on electric utility property have been deferred and will be amortized to income over the life of the related property. Additionally, OG&E earns federal tax credits associated with production from its wind facilities. Oklahoma production and investment state tax credits are also earned on investments in electric and solar generating facilities which further reduce OG&E's effective tax rate. The following schedule reconciles the statutory tax rates to the effective income tax rate: Year Ended December 31 2019 2018 2017 Statutory federal tax rate 21.0 % 21.0 % 35.0 % Federal renewable energy credit (A) (7.6) (6.9) (6.1) Amortization of net unfunded deferred taxes (5.6) (2.9) 0.9 State income taxes, net of federal income tax benefit (1.8) (0.2) 2.2 Other (0.6) (0.1) (0.3) Effective income tax rate 5.4 % 10.9 % 31.7 % (A) Represents credits associated with the production from OG&E's wind farms. The deferred tax provisions are recognized as costs in the ratemaking process by the commissions having jurisdiction over the rates charged by OG&E. The components of Deferred Income Taxes at December 31, 2019 and 2018 were as follows: December 31 (In millions) 2019 2018 Deferred income tax liabilities, net: Accelerated depreciation and other property related differences $ 1,656.8 $ 1,605.3 Regulatory assets 28.4 17.4 OG&E Pension Plan 24.5 26.0 Bond redemption-unamortized costs 2.2 2.4 Federal tax credits (238.0) (237.5) Income taxes recoverable from customers, net (229.9) (239.6) State tax credits (170.8) (142.3) Regulatory liabilities (68.1) (78.8) Asset retirement obligations (19.2) (21.5) Postretirement medical and life insurance benefits (16.0) (16.2) Net operating losses (5.7) (10.0) Other (4.7) (2.4) Accrued liabilities (4.3) (6.1) Deferred federal investment tax credits (1.8) (1.9) Accrued vacation (1.6) (1.7) Uncollectible accounts (0.4) (0.4) Total deferred income tax liabilities, net $ 951.4 $ 892.7 As of December 31, 2019, OG&E has classified $16.4 million of unrecognized tax benefits as a reduction of deferred tax assets recorded. Management is currently unaware of any issues under review that could result in significant additional payments, accruals or other material deviation from this amount. Following is a reconciliation of OG&E’s total gross unrecognized tax benefits as of the years ended December 31, 2019, 2018 and 2017. (In millions) 2019 2018 2017 Balance at January 1 $ 20.7 $ 20.7 $ 20.7 Tax positions related to current year: Additions — — — Balance at December 31 $ 20.7 $ 20.7 $ 20.7 As of each of December 31, 2019, 2018 and 2017, there were $16.4 million of unrecognized tax benefits that, if recognized, would affect the annual effective tax rate. Where applicable, OG&E classifies income tax-related interest and penalties as interest expense and other expense, respectively. During the year ended December 31, 2019, there were no income tax-related interest or penalties recorded with regard to uncertain tax positions. OG&E sustained federal and state tax operating losses through 2012 caused primarily by bonus depreciation and other book versus tax temporary differences. As a result, OG&E had accrued federal and state income tax benefits carrying into 2017, when the remaining federal net operating loss was utilized. State operating losses are being carried forward for utilization in future years. In addition to the tax operating losses, OG&E was unable to utilize the various tax credits that were generated during these years. These tax losses and credits are being carried as deferred tax assets and will be utilized in future periods. Under current law, OG&E anticipates future taxable income will be sufficient to utilize remaining losses and credits before they begin to expire after 2020. The following table summarizes these carry forwards: (In millions) Carry Forward Amount Deferred Tax Asset Earliest Expiration Date State operating loss $ 127.3 $ 5.7 2030 Federal tax credits $ 238.0 $ 238.0 2032 State tax credits: Oklahoma investment tax credits $ 165.1 $ 130.4 N/A Oklahoma capital investment board credits $ 12.4 $ 12.4 N/A Oklahoma zero emission tax credits $ 34.9 $ 28.0 2020 N/A - not applicable

Common Stock and Cumulative Pre

Common Stock and Cumulative Preferred Stock	9 Months Ended
	Sep. 30, 2019
Common Stock and Cumulative Preferred Stock [Abstract]
Common Stock and Cumulative Preferred Stock [Text Block]	Common Stock and Cumulative Preferred Stock There were no new shares of common stock issued in 2019, 2018 or 2017.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2019
Long-term Debt, Unclassified [Abstract]
Long-Term Debt	Long-Term Debt A summary of OG&E's long-term debt is included in the Statements of Capitalization. OG&E has no long-term debt maturing in the next five years. At December 31, 2019, OG&E was in compliance with all of its debt agreements. OG&E has previously incurred costs related to debt refinancing. Unamortized loss on reacquired debt is classified as a Non-Current Regulatory Asset. Unamortized debt expense and unamortized premium and discount on long-term debt are classified as Long-Term Debt in the Balance Sheets and are being amortized over the life of the respective debt. Industrial Authority Bonds OG&E has tax-exempt pollution control bonds with optional redemption provisions that allow the holders to request repayment of the bonds on any business day. The bonds, which can be tendered at the option of the holder during the next 12 months, are as follows: Series Date Due Amount (In millions) 1.20% - 2.50% Garfield Industrial Authority, January 1, 2025 $ 47.0 1.19% - 2.35% Muskogee Industrial Authority, January 1, 2025 32.4 1.20% - 2.48% Muskogee Industrial Authority, June 1, 2027 56.0 Total (redeemable during next 12 months) $ 135.4 All of these bonds are subject to an optional tender at the request of the holders, at 100 percent of the principal amount, together with accrued and unpaid interest to the date of purchase. The bond holders, on any business day, can request repayment of the bond by delivering an irrevocable notice to the tender agent stating the principal amount of the bond, payment instructions for the purchase price and the business day the bond is to be purchased. The repayment option may only be exercised by the holder of a bond for the principal amount. When a tender notice has been received by the trustee, a third-party remarketing agent for the bonds will attempt to remarket any bonds tendered for purchase. This process occurs once per week. Since the original issuance of these series of bonds in 1995 and 1997, the remarketing agent has successfully remarketed all tendered bonds. If the remarketing agent is unable to remarket any such bonds, OG&E is obligated to repurchase such unremarketed bonds. As OG&E has both the intent and ability to refinance the bonds on a long-term basis and such ability is supported by an ability to consummate the refinancing, the bonds are classified as Long-Term Debt in OG&E's Financial Statements. OG&E believes that it has sufficient liquidity to meet these obligations. Issuance of Long-Term Debt In June 2019, OG&E issued $300.0 million of 3.30 percent senior notes due March 15, 2030. The proceeds from the issuance were added to OG&E's general funds to be used for general corporate purposes, including to repay short-term debt (including debt pertaining to the acquisition of the River Valley plant) and to fund ongoing capital expenditures and working capital.

Short-Term Debt and Credit Faci

Short-Term Debt and Credit Facility	12 Months Ended
	Dec. 31, 2019
Short-term Debt [Abstract]
Short-Term Debt and Credit Facility	Short-Term Debt and Credit Facility OG&E has a $450.0 million revolving credit facility that matures on March 8, 2023. This facility is available to back up OG&E's commercial paper borrowings, to provide revolving credit borrowings and can also be used as a letter of credit facility. At December 31, 2019, there were $0.3 million supporting letters of credit at a weighted-average interest rate of 1.00 percent. There were no outstanding commercial paper borrowings at December 31, 2019. OG&E's credit facility has a financial covenant requiring that OG&E maintain a maximum debt to capitalization ratio of 65 percent, as defined in the facility. OG&E's facility also contains covenants which restrict, among other things, mergers and consolidations, sales of all or substantially all assets, incurrence of liens and transactions with affiliates. OG&E's facility is subject to acceleration upon the occurrence of any default, including, among others, payment defaults on such facility, breach of representations, warranties and covenants, acceleration of indebtedness (other than intercompany and non-recourse indebtedness) of $100.0 million or more in the aggregate, change of control (as defined in the facility), nonpayment of uninsured judgments in excess of $100.0 million and the occurrence of certain Employee Retirement Income Security Act and bankruptcy events, subject where applicable to specified cure periods. At December 31, 2019, there were $304.8 million in advances to OGE Energy compared to $319.5 million at December 31, 2018. OG&E has an intercompany borrowing agreement with OGE Energy whereby OG&E has access to up to $350.0 million of OGE Energy's revolving credit amount. This agreement has a termination date of March 8, 2023. At December 31, 2019, there were no intercompany borrowings under this agreement. OGE Energy's and OG&E's ability to access the commercial paper market could be adversely impacted by a credit ratings downgrade or major market disruptions. Pricing grids associated with OGE Energy's and OG&E's credit facilities could cause annual fees and borrowing rates to increase if an adverse rating impact occurs. The impact of any future downgrade could include an increase in the costs of OGE Energy's and OG&E's short-term borrowings, but a reduction in OGE Energy's and OG&E's credit ratings would not result in any defaults or accelerations. Any future downgrade of OGE Energy or OG&E could also lead to higher long-term borrowing costs and, if below investment grade, would require OG&E to post collateral or letters of credit.

Retirement Plans and Postretire

Retirement Plans and Postretirement Benefit Plans	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
Pension and Other Postretirement Benefits Disclosure [Text Block]	Retirement Plans and Postretirement Benefit Plans Pension Plan and Restoration of Retirement Income Plan OG&E's employees participate in OGE Energy's Pension Plan and Restoration of Retirement Income Plan. It is OGE Energy's policy to fund the Pension Plan on a current basis based on the net periodic pension expense as determined by OGE Energy's actuarial consultants. Such contributions are intended to provide not only for benefits attributed to service to date but also for those expected to be earned in the future. OGE Energy made a $20.0 million and $15.0 million contribution to its Pension Plan in 2019 and 2018, of which $5.0 million is related to OG&E in both 2019 and 2018. OGE Energy has not determined whether it will need to make any contributions to the Pension Plan in 2020. Any contribution to the Pension Plan during 2020 would be a discretionary contribution, anticipated to be in the form of cash, and is not required to satisfy the minimum regulatory funding requirement specified by the Employee Retirement Income Security Act of 1974, as amended. OGE Energy could be required to make additional contributions if the value of its pension trust and postretirement benefit plan trust assets are adversely impacted by a major market disruption in the future. In accordance with ASC Topic 715, "Compensation - Retirement Benefits," a one-time settlement charge is required to be recorded by an organization when lump sum payments or other settlements that relieve the organization from the responsibility for the pension benefit obligation during the plan year exceed the service cost and interest cost components of the organization's net periodic pension cost. During 2019, 2018 and 2017, OG&E experienced an increase in both the number of employees electing to retire and the amount of lump sum payments paid to such employees upon retirement, which resulted in OG&E recording pension plan settlement charges as presented in the net periodic benefit cost table below. The pension settlement charges did not require a cash outlay by OG&E and did not increase OG&E's total pension expense over time, as the charges were an acceleration of costs that otherwise would be recognized as pension expense in future periods. OGE Energy provides a Restoration of Retirement Income Plan to those participants in OGE Energy's Pension Plan whose benefits are subject to certain limitations of the Code. Participants in the Restoration of Retirement Income Plan receive the same benefits that they would have received under OGE Energy's Pension Plan in the absence of limitations imposed by the federal tax laws. The Restoration of Retirement Income Plan is intended to be an unfunded plan. Obligations and Funded Status The following table presents the status of OGE Energy's Pension Plan, the Restoration of Retirement Income Plan and the postretirement benefit plans for 2019 and 2018. These amounts have been recorded in Accrued Benefit Obligations with the offset recorded as a regulatory asset in OG&E's Balance Sheets as discussed in Note 1. The regulatory asset represents a net periodic benefit cost to be recognized in the Statements of Income in future periods. OG&E's portion of the benefit obligation for OGE Energy's Pension Plan and the Restoration of Retirement Income Plan represents the projected benefit obligation, while the benefit obligation for the postretirement benefit plans represents the accumulated postretirement benefit obligation. The accumulated postretirement benefit obligation for OG&E's Pension Plan and Restoration of Retirement Income Plan differs from the projected benefit obligation in that the former includes no assumption about future compensation levels. The accumulated postretirement benefit obligation for the Pension Plan and the Restoration of Retirement Income Plan at December 31, 2019 was $425.8 million and $4.8 million, respectively. The accumulated postretirement benefit obligation for the Pension Plan and the Restoration of Retirement Income Plan at December 31, 2018 was $417.6 million and $5.0 million, respectively. The details of the funded status of the Pension Plan, the Restoration of Retirement Income Plan and the postretirement benefit plans and the amounts included in the Balance Sheets are included in the following table. Pension Plan Restoration of Retirement Postretirement December 31 (In millions) 2019 2018 2019 2018 2019 2018 Change in benefit obligation Beginning obligations $ 453.6 $ 510.6 $ 6.0 $ 4.2 $ 104.8 $ 115.8 Service cost 9.0 9.8 0.2 0.2 0.2 0.2 Interest cost 15.6 17.6 0.2 0.2 4.3 4.2 Plan settlements (45.6) (52.6) (0.9) (0.6) — — Participants' contributions — — — — 3.0 2.9 Actuarial losses (gains) 42.1 (19.0) 0.6 2.0 2.2 (6.5) Benefits paid (12.7) (12.8) — — (9.8) (11.8) Ending obligations $ 462.0 $ 453.6 $ 6.1 $ 6.0 $ 104.7 $ 104.8 Change in plans' assets Beginning fair value $ 387.6 $ 477.2 $ — $ — $ 40.6 $ 45.2 Actual return on plans' assets 64.8 (29.2) — — 4.0 (0.5) Employer contributions 5.0 5.0 0.9 0.6 4.1 4.8 Plan settlements (45.6) (52.6) (0.9) (0.6) — — Participants' contributions — — — — 3.0 2.9 Benefits paid (12.7) (12.8) — — (9.8) (11.8) Ending fair value $ 399.1 $ 387.6 $ — $ — $ 41.9 $ 40.6 Funded status at end of year $ (62.9) $ (66.0) $ (6.1) $ (6.0) $ (62.8) $ (64.2) Net Periodic Benefit Cost The following table presents the net periodic benefit cost components, before consideration of capitalized amounts, of OG&E's Pension Plan, Restoration of Retirement Income Plan and postretirement benefit plans that are included in the Financial Statements. Service cost is presented within Other Operation and Maintenance, and interest cost, expected return on plan assets, amortization of net loss, amortization of unrecognized prior service cost and settlement cost are presented within Other Net Periodic Benefit Expense in OG&E's Statements of Income. OG&E recovers specific amounts of pension and postretirement medical costs in rates approved in its Oklahoma rate reviews. In accordance with approved orders, OG&E defers the difference between actual pension and postretirement medical expenses and the amount approved in its last Oklahoma rate review as a regulatory asset or regulatory liability. These amounts have been recorded in the Pension tracker in the regulatory assets and liabilities table in Note 1 and within Other Net Periodic Benefit Expense in OG&E's Statements of Income. Pension Plan Restoration of Retirement Postretirement Benefit Plans Year Ended December 31 (In millions) 2019 2018 2017 2019 2018 2017 2019 2018 2017 Service cost $ 9.0 $ 9.8 $ 10.1 $ 0.2 $ 0.2 $ 0.1 $ 0.2 $ 0.2 $ 0.4 Interest cost 15.6 17.6 19.5 0.2 0.2 0.2 4.3 4.2 5.6 Expected return on plan assets (27.6) (33.1) (32.8) — — — (1.7) (1.8) (2.0) Amortization of net loss 12.9 12.1 13.0 0.3 0.5 0.4 2.1 3.8 1.9 Amortization of unrecognized prior service cost (A) — — — — — — (6.1) (6.1) (2.5) Settlement cost 16.4 19.4 11.7 0.5 0.4 — — — 0.4 Total net periodic benefit cost 26.3 25.8 21.5 1.2 1.3 0.7 (1.2) 0.3 3.8 Plus: Amount allocated from OGE Energy 4.5 5.7 — 0.5 1.2 — (0.6) (0.7) — Net periodic benefit cost $ 30.8 $ 31.5 $ 21.5 $ 1.7 $ 2.5 $ 0.7 $ (1.8) $ (0.4) $ 3.8 (A) Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment. In addition to the net periodic benefit cost amounts recognized, as presented in the table above, for the Pension and Restoration of Retirement Income Plans in 2019, 2018 and 2017, OG&E recognized the following: Year Ended December 31 (In millions) 2019 2018 2017 Decrease of pension expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ (16.1) $ (14.1) $ (2.3) Deferral of pension expense related to pension settlement charges: Oklahoma jurisdiction (A) $ 17.9 $ 22.1 $ 13.2 Arkansas jurisdiction (A) $ 1.7 $ 2.1 $ 1.1 (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1. In addition to the net periodic benefit income and cost amounts recognized, as presented in the table above, for the postretirement benefit plans in 2019, 2018 and 2017, OG&E recognized the following: Year Ended December 31 ( In millions ) 2019 2018 2017 Increase of postretirement expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ 1.0 $ 4.4 $ 6.2 (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1. (In millions) 2019 2018 2017 Capitalized portion of net periodic pension benefit cost $ 3.0 $ 3.2 $ 3.4 Capitalized portion of net periodic postretirement benefit cost $ 0.1 $ 0.1 $ 1.1 Rate Assumptions Pension Plan and Postretirement Year Ended December 31 2019 2018 2017 2019 2018 2017 Assumptions to determine benefit obligations: Discount rate 3.15 % 4.20 % 3.60 % 3.25 % 4.30 % 3.70 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A N/A Assumptions to determine net periodic benefit cost: Discount rate 3.63 % 3.73 % 4.00 % 4.30 % 3.70 % 4.20 % Expected return on plan assets 7.50 % 7.50 % 7.50 % 4.00 % 4.00 % 4.00 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A 4.20 % N/A - not applicable The discount rate used to compute the present value of plan liabilities is based generally on rates of high-grade corporate bonds with maturities similar to the average period over which benefits will be paid. The discount rate used to determine net benefit cost for the current year is the same discount rate used to determine the benefit obligation as of the previous year's balance sheet date, unless a plan settlement occurs during the current year that requires an updated discount rate for net periodic cost measurement. For 2019 and 2018, the Pension Plan discount rates used to determine net periodic benefit cost are disclosed on a weighted-average basis. The overall expected rate of return on plan assets assumption was 7.50 percent in both 2019 and 2018, which was used in determining net periodic benefit cost due to recent returns on OGE Energy's long-term investment portfolio. The rate of return on plan assets assumption is the average long-term rate of earnings expected on the funds currently invested and to be invested for the purpose of providing benefits specified by the Pension Plan or postretirement benefit plans. This assumption is reexamined at least annually and updated as necessary. The rate of return on plan assets assumption reflects a combination of historical return analysis, forward-looking return expectations and the plans' current and expected asset allocation. The assumed health care cost trend rates have a significant effect on the amounts reported for postretirement medical benefit plans. Future health care cost trend rates are assumed to be 7.00 percent in 2020 with the rates trending downward to 4.50 percent by 2030. The effects of a one-percentage point change in the assumed health care cost trend rate are presented in the following tables. ONE-PERCENTAGE POINT INCREASE Year Ended December 31 (In millions) 2019 2018 2017 Effect on aggregate of the service and interest cost components $ — $ — $ — Effect on accumulated postretirement benefit obligations $ 0.1 $ 0.1 $ 0.1 ONE-PERCENTAGE POINT DECREASE Year Ended December 31 (In millions) 2019 2018 2017 Effect on aggregate of the service and interest cost components $ — $ — $ — Effect on accumulated postretirement benefit obligations $ 0.2 $ 0.2 $ 0.2 Pension Plan Pension Plan Investments, Policies and Strategies The Pension Plan assets are held in a trust which follows an investment policy and strategy designed to reduce the funded status volatility of the Plan by utilizing liability driven investing. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The investment policy follows a glide path approach that shifts a higher portfolio weighting to fixed income as the Plan's funded status increases. The table below sets forth the targeted fixed income and equity allocations at different funded status levels. Projected Benefit Obligation Funded Status Thresholds <90% 95% 100% 105% 110% 115% 120% Fixed income 50% 58% 65% 73% 80% 85% 90% Equity 50% 42% 35% 27% 20% 15% 10% Total 100% 100% 100% 100% 100% 100% 100% Within the portfolio's overall allocation to equities, the funds are allocated according to the guidelines in the table below. Asset Class Target Allocation Minimum Maximum Domestic Large Cap Equity 40% 35% 60% Domestic Mid-Cap Equity 15% 5% 25% Domestic Small-Cap Equity 25% 5% 30% International Equity 20% 10% 30% OGE Energy has retained an investment consultant responsible for the general investment oversight, analysis, monitoring investment guideline compliance and providing quarterly reports to certain of OG&E's members and OGE Energy's Investment Committee. The various investment managers used by the trust operate within the general operating objectives as established in the investment policy and within the specific guidelines established for each investment manager's respective portfolio. The portfolio is rebalanced at least on an annual basis to bring the asset allocations of various managers in line with the target asset allocation listed above. More frequent rebalancing may occur if there are dramatic price movements in the financial markets which may cause the trust's exposure to any asset class to exceed or fall below the established allowable guidelines. To evaluate the progress of the portfolio, investment performance is reviewed quarterly. It is, however, expected that performance goals will be met over a full market cycle, normally defined as a three to five year period. Analysis of performance is within the context of the prevailing investment environment and the advisors' investment style. The goal of the trust is to provide a rate of return consistently from three percent to five percent over the rate of inflation (as measured by the national Consumer Price Index) on a fee adjusted basis over a typical market cycle of no less than three years and no more than five years. Each investment manager is expected to outperform its respective benchmark. Below is a list of each asset class utilized with appropriate comparative benchmark(s) each manager is evaluated against: Asset Class Comparative Benchmark(s) Active Duration Fixed Income Bloomberg Barclays Aggregate Long Duration Fixed Income Duration blended Barclays Long Government/Credit & Barclays Universal Equity Index Standard & Poor's 500 Index Mid-Cap Equity Russell Midcap Index Russell Midcap Value Index Small-Cap Equity Russell 2000 Index Russell 2000 Value Index International Equity Morgan Stanley Capital International ACWI ex-U.S. The fixed income managers are expected to use discretion over the asset mix of the trust assets in their efforts to maximize risk-adjusted performance. Exposure to any single issuer, other than the U.S. government, its agencies or its instrumentalities (which have no limits), is limited to five percent of the fixed income portfolio as measured by market value. At least 75 percent of the invested assets must possess an investment-grade rating at or above Baa3 or BBB- by Moody's Investors Service, S&P's Global Ratings or Fitch Ratings. The portfolio may invest up to 10 percent of the portfolio's market value in convertible bonds as long as the securities purchased meet the quality guidelines. A portfolio may invest up to 15 percent of the portfolio's market value in private placement, including 144A securities with or without registration rights and allow for futures to be traded in the portfolio. The purchase of any of OGE Energy's equity, debt or other securities is prohibited. The domestic value equity managers focus on stocks that the manager believes are undervalued in price and earn an average or less than average return on assets and often pays out higher than average dividend payments. The domestic growth equity manager will invest primarily in growth companies which consistently experience above average growth in earnings and sales, earn a high return on assets and reinvest cash flow into existing business. The domestic mid-cap equity portfolio manager focuses on companies with market capitalizations lower than the average company traded on the public exchanges with the following characteristics: price/earnings ratio at or near the Russell Midcap Index, small dividend yield, return on equity at or near the Russell Midcap Index and an earnings per share growth rate at or near the Russell Midcap Index. The domestic small-cap equity manager will purchase shares of companies with market capitalizations lower than the average company traded on the public exchanges with the following characteristics: price/earnings ratio at or near the Russell 2000, small dividend yield, return on equity at or near the Russell 2000 and an earnings per share growth rate at or near the Russell 2000. The international global equity manager invests primarily in non-dollar denominated equity securities. Investing internationally diversifies the overall trust across the global equity markets. The manager is required to operate under certain restrictions including regional constraints, diversification requirements and percentage of U.S. securities. The Morgan Stanley Capital International All Country World ex-U.S. Index is the benchmark for comparative performance purposes. The Morgan Stanley Capital International All Country World ex-U.S. Index is a market value weighted index designed to measure the combined equity market performance of developed and emerging markets countries, excluding the U.S. All of the equities which are purchased for the international portfolio are thoroughly researched. All securities are freely traded on a recognized stock exchange, and there are no over-the-counter derivatives. The following investment categories are excluded: options (other than traded currency options), commodities, futures (other than currency futures or currency hedging), short sales/margin purchases, private placements, unlisted securities and real estate (but not real estate shares). For all domestic equity investment managers, no more than five percent can be invested in any one stock at the time of purchase and no more than 10 percent after accounting for price appreciation. Options or financial futures may not be purchased unless prior approval of OGE Energy's Investment Committee is received. The purchase of securities on margin is prohibited as is securities lending. Private placement or venture capital may not be purchased. All interest and dividend payments must be swept on a daily basis into a short-term money market fund for re-deployment. The purchase of any of OGE Energy's equity, debt or other securities is prohibited. The purchase of equity or debt issues of the portfolio manager's organization is also prohibited. The aggregate positions in any company may not exceed one percent of the fair market value of its outstanding stock. Pension Plan Investments The following tables summarize OG&E's portion of OGE Energy's Pension Plan's investments that are measured at fair value on a recurring basis at December 31, 2019 and 2018. There were no Level 3 investments held by the Pension Plan at December 31, 2019 and 2018. (In millions) December 31, 2019 Level 1 Level 2 Net Asset Value (A) Common stocks $ 202.0 $ 202.0 $ — $ — U.S. Treasury notes and bonds (B) 134.8 134.8 — — Mortgage- and asset-backed securities 45.8 — 45.8 — Corporate fixed income and other securities 130.5 — 130.5 — Commingled fund (C) 23.9 — — 23.9 Foreign government bonds 3.0 — 3.0 — U.S. municipal bonds 1.1 — 1.1 — Money market fund 7.5 — — 7.5 Mutual fund 2.4 2.4 — — Preferred stocks 0.7 0.7 — — Futures: U.S. Treasury futures (receivable) 22.9 — 22.9 — U.S. Treasury futures (payable) (10.9) — (10.9) — Cash collateral 0.6 0.6 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 564.4 $ 340.5 $ 192.5 $ 31.4 Interest and dividends receivable 2.4 Payable to broker for securities purchased (36.5) Pension Plan investments attributable to affiliates (131.2) Total Pension Plan assets $ 399.1 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. (In millions) December 31, 2018 Level 1 Level 2 Net Asset Value (A) Common stocks $ 169.3 $ 169.3 $ — $ — U.S. Treasury notes and bonds (B) 137.9 137.9 — — Mortgage- and asset-backed securities 65.9 — 65.9 — Corporate fixed income and other securities 143.2 — 143.2 — Commingled fund (C) 19.7 — — 19.7 Foreign government bonds 4.4 — 4.4 — U.S. municipal bonds 0.6 — 0.6 — Money market fund 0.3 — — 0.3 Mutual fund 8.0 8.0 — — Futures: U.S. Treasury futures (receivable) 27.0 — 27.0 — U.S. Treasury futures (payable) (20.4) — (20.4) — Cash collateral 0.7 0.7 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 556.7 $ 315.9 $ 220.8 $ 20.0 Interest and dividends receivable 3.0 Payable to broker for securities purchased (36.9) Pension Plan investments attributable to affiliates (135.2) Total Pension Plan assets $ 387.6 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. As defined in the fair value hierarchy, Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible by the Pension Plan at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the Plan's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). Expected Benefit Payments The following table summarizes the benefit payments OG&E expects to pay related to OGE Energy's Pension Plan and Restoration of Retirement Income Plan. These expected benefits are based on the same assumptions used to measure OGE Energy's benefit obligation at the end of the year and include benefits attributable to estimated future employee service. (In millions) Projected Benefit Payments 2020 $ 44.6 2021 $ 44.2 2022 $ 42.5 2023 $ 42.2 2024 $ 42.0 After 2024 $ 179.8 Postretirement Benefit Plans In addition to providing pension benefits, OGE Energy provides certain medical and life insurance benefits for eligible retired members. Regular, full-time, active employees hired prior to February 1, 2000 whose age and years of credited service total or exceed 80 or have attained at least age 55 with 10 or more years of service at the time of retirement are entitled to postretirement medical benefits, while employees hired on or after February 1, 2000 are not entitled to postretirement medical benefits. Eligible retirees must contribute such amount as OGE Energy specifies from time to time toward the cost of coverage for postretirement benefits. The benefits are subject to deductibles, co-payment provisions and other limitations. OG&E charges postretirement benefit costs to expense and includes an annual amount as a component of the cost-of-service in future ratemaking proceedings. OGE Energy's contribution to the medical costs for pre-65 aged eligible retirees are fixed at the 2011 level, and OGE Energy covers future annual medical inflationary cost increases up to five percent. Increases in excess of five percent annually are covered by the pre-65 aged retiree in the form of premium increases. OGE Energy provides Medicare-eligible retirees and their Medicare-eligible spouses an annual fixed contribution to OGE Energy's sponsored health reimbursement arrangement. OGE Energy's Medicare-eligible retirees are able to purchase individual insurance policies supplemental to Medicare through a third-party administrator and use their health reimbursement arrangement funds for reimbursement of medical premiums and other eligible medical expenses. Postretirement Plans Investments The following tables summarize OG&E's portion of OGE Energy's postretirement benefit plans' investments that are measured at fair value on a recurring basis at December 31, 2019 and 2018. There were no Level 2 investments held by the postretirement benefit plans at December 31, 2019 and 2018. (In millions) December 31, 2019 Level 1 Level 3 Group retiree medical insurance contract $ 34.8 $ — $ 34.8 Mutual funds 10.9 10.9 — Money market fund 1.2 1.2 — Total plan investments 46.9 $ 12.1 $ 34.8 Plan investments attributable to affiliates (5.0) Total plan assets $ 41.9 (In millions) December 31, 2018 Level 1 Level 3 Group retiree medical insurance contract $ 36.0 $ — $ 36.0 Mutual funds 8.9 8.9 — Cash 0.9 0.9 — Total plan investments 45.8 $ 9.8 $ 36.0 Plan investments attributable to affiliates (5.2) Total plan assets $ 40.6 The group retiree medical insurance contract invests in a pool of common stocks, bonds and money market accounts, of which a significant portion is comprised of mortgage-backed securities. The unobservable input included in the valuation of the contract includes the approach for determining the allocation of the postretirement benefit plans' pro-rata share of the total assets in the contract. The following table summarizes the postretirement benefit plans' investments that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Year Ended December 31 (In millions) 2019 Group retiree medical insurance contract: Beginning balance $ 36.0 Claims paid (3.8) Investment fees (0.1) Net unrealized gains related to instruments held at the reporting date 1.4 Interest income 0.8 Dividend income 0.5 Ending balance $ 34.8 Medicare Prescription Drug, Improvement and Modernization Act of 2003 The Medicare Prescription Drug, Improvement and Modernization Act of 2003 expanded coverage for prescription drugs. The following table summarizes the gross benefit payments OG&E expects to pay related to its postretirement benefit plans, including prescription drug benefits. (In millions) Gross Projected 2020 $ 8.9 2021 $ 8.9 2022 $ 8.8 2023 $ 7.4 2024 $ 7.3 After 2024 $ 32.4 Post-Employment Benefit Plan Disabled employees receiving benefits from OGE Energy's Group Long-Term Disability Plan are entitled to continue participating in OGE Energy's Medical Plan along with their dependents. The post-employment benefit obligation represents the actuarial present value of estimated future medical benefits that are attributed to employee service rendered prior to the date as of which such information is presented. The obligation also includes future medical benefits expected to be paid to current employees participating in OGE Energy's Group Long-Term Disability Plan and their dependents, as defined in OGE Energy's Medical Plan. The post-employment benefit obligation is determined by an actuary on a basis similar to the accumulated postretirement benefit obligation. The estimated future medical benefits are projected to grow with expected future medical cost trend rates and are discounted for interest at the discount rate and for the probability that the participant will discontinue receiving benefits from OGE Energy's Group Long-Term Disability Plan due to death, recovery from disability or eligibility for retiree medical benefits. OG&E's post-employment benefit obligation was $1.7 million at both December 31, 2019 and 2018. 401(k) Plan OGE Energy provides a 401(k) Plan, and each regular full-time employee of OGE Energy or a participating affiliate is eligible to participate in the 401(k) Plan immediately. All other employees of OGE Energy or a participating affiliate are eligible to become participants in the 401(k) Plan after completing one year of service as defined in the 401(k) Plan. Participants may contribute each pay period any whole percentage between two percent and 19 percent of their compensation, as defined in the 401(k) Plan, for that pay period. Participants who have reached age 50 before the close of a year are allowed to make additional contributions referred to as "Catch-Up Contributions," subject to certain limitations of the Code. Participants may designate, at their discretion, all or any portion of their contributions as: (i) a before-tax contribution under Section 401(k) of the Code subject to the limitations thereof, (ii) a contribution made on a non-Roth after-tax basis or (iii) a Roth contribution. The 401(k) Plan also includes an eligible automatic contribution arrangement and provides for a qualified default investment alternative consistent with the U.S. Department of Labor regulations. Participants may elect, in accordance with the 401(k) Plan procedures, to have their future salary deferral rate to be automatically increased annually on a date and in an amount as specified by the participant in such election. For employees hired or rehired on or after December 1, 2009, OGE Energy contributes to the 401(k) Plan, on behalf of each participant, 200 percent of the participant's contributions up to five percent of compensation. No OGE Energy contributions are made with respect to a participant's Catch-Up Contributions, rollover contributions or with respect to a participant's contributions based on overtime payments, pay-in-lieu of overtime for exempt personnel, special lump-sum recognition awards and lump-sum merit awards included in compensation for determining the amount of participant contributions. Once made, OGE Energy's contribution may be directed to any available investment option in the 401(k) Plan. OGE Energy match contributions vest over a three-year period. After two years of service, participants become 20 percent vested in their OGE Energy contribution account and become fully vested on completing three years of service. In addition, participants fully vest when they are eligible for normal or early retirement under the Pension Plan requirements, in the event of their termination due to death or permanent disability or upon attainment of age 65 while employed by OGE Energy or its affiliates. OG&E contributed $11.0 million, $9.8 million and $9.7 million in 2019, 2018 and 2017, respectively, to the 401(k) Plan. Deferred Compensation Plan OGE Energy provides a nonqualified deferred compensation plan which is intended to be an unfunded plan. The plan's primary purpose is to provide a tax-deferred capital accumulation vehicle for a select group of management, highly compensated employees and non-employee members of the Board of Directors of OGE Energy and to supplement such employees' 401(k) Plan contributions as well as offering this plan to be competitive in the marketplace. Eligible employees who enroll in the plan have the following deferral options: (i) eligible employees may elect to defer up to a maximum of 70 percent of base salary and 100 percent of annual bonus awards or (ii) eligible employees may elect a deferral percentag

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Public Utility Regulatory Policy Act of 1978 OG&E had a QF contract with AES which expired on January 15, 2019 and a QF contract with Oklahoma Cogeneration LLC which expired on August 31, 2019. For the 320 MW AES QF contract and the 120 MW Oklahoma Cogeneration LLC QF contract, OG&E purchased 100 percent of the electricity generated by the QFs. In December 2018, OG&E announced its plan to acquire power plants from AES and Oklahoma Cogeneration LLC, pending regulatory approval, to meet customers' energy needs. In May 2019, OG&E received the necessary approval from the OCC and the FERC and conditional approval from the APSC to acquire both plants. In May 2019, OG&E acquired the power plant from AES, and in August 2019, OG&E acquired the power plant from Oklahoma Cogeneration LLC. In August 2019, OG&E received final approval from the APSC to acquire both plants. Further discussion can be found in Note 15. For the years ended December 31, 2019, 2018 and 2017, OG&E made total payments to cogenerators of $14.7 million, $112.4 million and $115.2 million, respectively, of which $7.4 million, $60.0 million and $63.0 million, respectively, represented capacity payments. All payments for purchased power, including cogeneration, are included in the Statements of Income as Cost of Sales. Purchase Obligations and Commitments OG&E's future purchase obligations and commitments estimated for the next five years are as follows: (In millions) 2020 2021 2022 2023 2024 Total Purchase obligations and commitments: Minimum purchase commitments $ 82.6 $ 55.1 $ 50.4 $ 50.4 $ 32.9 $ 271.4 Expected wind purchase commitments 55.7 56.0 56.4 56.8 57.5 282.4 Long-term service agreement commitments 2.4 2.4 2.4 13.8 32.1 53.1 Environmental compliance plan expenditures 0.4 — — — — 0.4 Total purchase obligations and commitments $ 141.1 $ 113.5 $ 109.2 $ 121.0 $ 122.5 $ 607.3 Minimum Purchase Commitments OG&E has coal contracts for purchases through June 30, 2020 and May 31, 2021, whereby OG&E has the right but not the obligation to purchase a defined quantity of coal. OG&E purchases its coal through spot purchases on an as-needed basis. As a participant in the SPP Integrated Marketplace, OG&E purchases its natural gas supply through short-term agreements. OG&E relies on a combination of natural gas base load agreements and call agreements, whereby OG&E has the right but not the obligation to purchase a defined quantity of natural gas, combined with day and intra-day purchases to meet the demands of the SPP Integrated Marketplace. OG&E has natural gas transportation service contracts with Enable and ONEOK, Inc. The contract with Enable ends in May 2024, and the contract with ONEOK, Inc. ends in August 2037. These transportation contracts grant Enable and ONEOK, Inc. the responsibility of delivering natural gas to OG&E's generating facilities. Wind Purchase Commitments The following table summarizes OG&E's wind power purchase contracts. Company Location Original Term of Contract Expiration of Contract MWs CPV Keenan Woodward County, OK 20 years 2030 152.0 Edison Mission Energy Dewey County, OK 20 years 2031 130.0 NextEra Energy Blackwell, OK 20 years 2032 60.0 The following table summarizes OG&E's wind power purchases for the years ended December 31, 2019, 2018 and 2017. Year Ended December 31 (In millions) 2019 2018 2017 CPV Keenan $ 27.2 $ 27.0 $ 29.0 Edison Mission Energy 23.1 21.7 22.1 NextEra Energy 7.4 6.8 7.4 FPL Energy (A) — 2.1 2.6 Total wind power purchased $ 57.7 $ 57.6 $ 61.1 (A) OG&E's purchased power contract with FPL Energy for 50 MWs expired in 2018. Long-Term Service Agreement Commitments OG&E has a long-term parts and service maintenance contract for the upkeep of the McClain Plant. In May 2013, a new contract was signed that is expected to run for the earlier of 128,000 factored-fired hours or 4,800 factored-fired starts. In December 2015, the McClain Long-Term Service Agreement was amended to define the terms and conditions for the exchange of spare rotors between OG&E and General Electric International, Inc. Based on historical usage and current expectations for future usage, this contract is expected to run until 2033. The contract requires payments based on both a fixed and variable cost component, depending on how much the McClain Plant is used. OG&E has a long-term parts and service maintenance contract for the upkeep of the Redbud Plant. In March 2013, the contract was amended to extend the contract coverage for an additional 24,000 factored-fired hours resulting in a maximum of the earlier of 144,000 factored-fired hours or 4,500 factored-fired starts. Based on historical usage and current expectations for future usage, this contract is expected to run until 2030. The contract requires payments based on both a fixed and variable cost component, depending on how much the Redbud Plant is used. Environmental Laws and Regulations The activities of OG&E are subject to numerous stringent and complex federal, state and local laws and regulations governing environmental protection. These laws and regulations can change, restrict or otherwise impact OG&E's business activities in many ways, including the handling or disposal of waste material, planning for future construction activities to avoid or mitigate harm to threatened or endangered species and requiring the installation and operation of emissions or pollution control equipment. Failure to comply with these laws and regulations could result in the assessment of administrative, civil and criminal penalties, the imposition of remedial requirements and the issuance of orders enjoining future operations. Management believes that all of its operations are in substantial compliance with current federal, state and local environmental standards. Environmental regulation can increase the cost of planning, design, initial installation and operation of OG&E's facilities. Management continues to evaluate its compliance with existing and proposed environmental legislation and regulations and implement appropriate environmental programs in a competitive market. Affordable Clean Energy Rule On July 8, 2019, the EPA published the Affordable Clean Energy rule. Numerous parties, not including OG&E, have filed petitions for judicial review of the Affordable Clean Energy rule in the U.S. Court of Appeals for the District of Columbia Circuit. The Affordable Clean Energy rule requires states, including Oklahoma, to develop emission limitations for carbon dioxide for each existing coal-fired utility boiler within the state, including all of OG&E's coal units, and submit a compliance and implementation plan to the EPA by July 2022. The EPA will approve or disapprove the proposed state plan within 18 months of submittal and develop a federal implementation plan if the proposed state plan is disapproved. The ultimate timing and impact of these standards on OG&E's operations cannot be determined with certainty at this time, although a requirement for significant reduction of CO 2 emissions from existing fossil-fuel-fired power plants ultimately could result in significant additional compliance costs that would affect OG&E's future financial position, results of operations and cash flows if such costs are not recovered through regulated rates. Other In the normal course of business, OG&E is confronted with issues or events that may result in a contingent liability. These generally relate to lawsuits or claims made by third parties, including governmental agencies. When appropriate, management consults with legal counsel and other experts to assess the claim. If, in management's opinion, OG&E has incurred

Rate Matters and Regulation

Rate Matters and Regulation	12 Months Ended
	Dec. 31, 2019
Regulated Operations [Abstract]
Rate Matters and Regulation	Rate Matters and Regulation Regulation and Rates OG&E's retail electric tariffs are regulated by the OCC in Oklahoma and by the APSC in Arkansas. The issuance of certain securities by OG&E is also regulated by the OCC and the APSC. OG&E's transmission activities, short-term borrowing authorization and accounting practices are subject to the jurisdiction of the FERC. The Secretary of the U.S. Department of Energy has jurisdiction over some of OG&E's facilities and operations. In 2019, 86 percent of OG&E's electric revenue was subject to the jurisdiction of the OCC, eight percent to the APSC and six percent to the FERC. The OCC and the APSC require that, among other things, (i) OGE Energy permits the OCC and the APSC access to the books and records of OGE Energy and its affiliates relating to transactions with OG&E; (ii) OGE Energy employ accounting and other procedures and controls to protect against subsidization of non-utility activities by OG&E's customers; and (iii) OGE Energy refrain from pledging OG&E assets or income for affiliate transactions. In addition, the FERC has access to the books and records of OGE Energy and its affiliates as the FERC deems relevant to costs incurred by OG&E or necessary or appropriate for the protection of utility customers with respect to the FERC jurisdictional rates. Completed Regulatory Matters Arkansas 2018 Formula Rate Plan Filing Per OG&E's settlement in its last general rate review, OG&E filed an evaluation report under its Formula Rate Plan in October 2018. On March 6, 2019, the APSC approved a settlement agreement for a $3.3 million revenue increase, and new rates were effective as of April 1, 2019. Approval for Acquisition of Existing Power Plants In December 2018, OG&E filed an application for pre-approval from the OCC to acquire a 360 MW capacity coal- and natural gas-fired plant from AES and a 146 MW capacity natural gas-fired combined-cycle plant from Oklahoma Cogeneration LLC for $53.5 million. The purchase of these assets replaces capacity provided by purchased power contracts that expired in 2019 and helps OG&E satisfy its customers' energy needs and load obligations to the SPP. In addition, the filing sought approval of a rider mechanism to collect costs associated with the purchase of these generating facilities. On May 13, 2019, the OCC approved OG&E's acquisition of both plants, the requested rider mechanism for the AES plant and regulatory asset treatment for the Oklahoma Cogeneration LLC plant that will defer non-fuel operation and maintenance expenses, depreciation and ad valorem taxes. On January 23, 2019, OG&E filed an application for Federal Power Act Section 203 approval with a request for expedited consideration. This application requested FERC's prior authorization to acquire the AES and Oklahoma Cogeneration LLC plants. On May 22, 2019, OG&E received authorization from the FERC to acquire both plants. On April 24, 2019, OG&E filed an application with the APSC requesting approval of the acquisition, as well as depreciation rates, of the AES and Oklahoma Cogeneration LLC plants, and on May 8, 2019, OG&E received conditional approval for the purchase of the generating facilities. On August 30, 2019, the APSC issued an order finding that the plants to be acquired were used and useful and that the acquisition of the plants was in the public interest. The APSC also approved the depreciation rates to be applied to the acquired plants. The cost OG&E paid for the acquired plants was reviewed by the APSC in OG&E's 2019 Formula Rate Plan filing, and parties reached a settlement agreement requesting the APSC to approve the cost of the acquisitions. OG&E is awaiting a final decision from the APSC. In May 2019, OG&E completed the acquisition of the power plant from AES and placed it into service, which is now named the River Valley power plant. In August 2019, OG&E completed the acquisition of the power plant from Oklahoma Cogeneration LLC and placed it into service, which is now named the Frontier power plant. Fuel Adjustment Clause Review for Calendar Year 2017 In July 2018, the OCC staff filed an application to review OG&E's fuel adjustment clause for the calendar year 2017, including the prudence of OG&E's electric generation, purchased power and fuel procurement costs. On February 1, 2019, the Administrative Law Judge recommended that OG&E's processes, costs, investments and decisions regarding fuel procurement for the 2017 calendar year be found prudent. On May 22, 2019, the OCC deemed OG&E's electric generation, purchased power and fuel procurement costs to be materially prudent. Oklahoma Rate Review Filing - December 2018 In December 2018, OG&E filed a general rate review with the OCC, requesting a rate increase of $77.6 million per year to recover its investment in the Dry Scrubbers project and in the conversion of Muskogee Units 4 and 5 to natural gas, to align OG&E's return on equity more closely to the industry average and to align OG&E's depreciation rates to more realistically reflect its assets' lifespans. On May 24, 2019, OG&E entered into a non-unanimous joint stipulation and settlement agreement with the OCC staff, the Attorney General's Office of Oklahoma, the Oklahoma Industrial Energy Consumers and certain other parties associated with the requested rate increase. The filing was further amended on May 30, 2019 to include Oklahoma Association of Electric Cooperatives as a settling party. Under the terms of the settlement agreement, OG&E would receive full recovery of its environmental investments in the Dry Scrubbers project and in the conversion of Muskogee Units 4 and 5 to natural gas. Base rates would not change as a result of the settlement agreement due to the reduction of costs related to cogeneration contracts and the acceleration of unprotected deferred tax savings over a 10-year period. Further, OG&E's current depreciation rates and return on equity of 9.5 percent for purposes of calculating the allowance for funds used during construction and OG&E's various recovery riders that include a full return component would remain unchanged. On July 1, 2019, OG&E implemented interim rates, which were subject to refund of any amount recovered in excess of the rates ultimately approved by the OCC in the rate review. On September 19, 2019, the OCC issued a final order which approved the settlement agreement. The Dry Scrubbers project, which includes the installation of two dry scrubbers at the Sooner plant, and the conversion of Muskogee Units 4 and 5 to natural gas were initiated in response to the EPA's MATS and Regional Haze Rule FIP. The Dry Scrubber systems on Sooner Unit 1 and Unit 2 were placed into service in October 2018 and January 2019, respectively. Muskogee Units 4 and 5 were placed into service in March 2019. Fuel Adjustment Clause Review for Calendar Year 2018 In June 2019, the OCC staff filed an application to review OG&E's fuel adjustment clause for the calendar year 2018, including the prudence of OG&E's electric generation, purchased power and fuel procurement costs. On December 12, 2019, the OCC issued an order deeming OG&E's electric generation, purchased power and fuel procurement costs were prudent. FERC - Section 206 Filing In January 2018, the Oklahoma Municipal Power Authority filed a complaint at the FERC stating that the base return on common equity used by OG&E in calculating formula transmission rates under the SPP Open Access Transmission Tariff is unjust and unreasonable and should be reduced from 10.60 percent to 7.85 percent, effective upon the date of the complaint. In addition to the request to reduce the return on equity, the Oklahoma Municipal Power Authority's complaint also requests that modifications be made to OG&E's transmission formula rates to reflect the impacts of the 2017 Tax Act, including the 2017 Tax Act's impact on accumulated deferred income tax balances. In May 2019, all parties agreed to a settlement which provides for 10 percent base return on equity, plus a 50-basis point adder, and a five-year amortization period of the unprotected excess accumulated deferred income taxes associated with the 2017 Tax Act. On November 21, 2019, the FERC approved the settlement agreement. Pending Regulatory Matters Set forth below is a list of various proceedings pending before state or federal regulatory agencies. Unless stated otherwise, OG&E cannot predict when the regulatory agency will act or what action the regulatory agency will take. OG&E's financial results are dependent in part on timely and adequate decisions by the regulatory agencies that set OG&E's rates. FERC Order for Sponsored Transmission Upgrades within SPP Under the SPP Open Access Transmission Tariff, costs of participant-funded, or "sponsored," transmission upgrades may be recovered from other SPP customers whose transmission service depends on capacity enabled by the upgrade. The SPP Open Access Transmission Tariff required SPP to charge for these upgrades beginning in 2008, but SPP had not been charging its customers for these upgrades due to information system limitations. However, SPP had informed participants in the market that these charges would be forthcoming. In July 2016, the FERC granted SPP's request to recover the charges not billed since 2008. SPP subsequently billed OG&E for these charges and credited OG&E related to transmission upgrades that OG&E had sponsored, which resulted in OG&E being a net receiver of sponsored upgrade credits. The majority of these net credits were refunded to customers through OG&E's various rate riders that include SPP activity with the remaining amounts retained by OG&E. Several companies that were net payers of Z2 charges sought rehearing of the FERC's July 2016 order; however, in November 2017, the FERC denied the rehearing requests. In January 2018, one of the impacted companies appealed the FERC's decision to the U.S. Court of Appeals for the District of Columbia Circuit. In July 2018, that court granted a motion requested by the FERC that the case be remanded back to the FERC for further examination and proceedings. In February 2019, the FERC reversed its July 2016 order and November 2017 rehearing denial, ruled that SPP violated its tariff to charge for the 2008 - 2015 period in 2016, held that the SPP tariff provision that prohibited those charges could not be waived and ordered SPP to develop a plan to refund the payments but not to implement the refunds until further ordered to do so. In response, on April 1, 2019, OG&E filed a request for rehearing with the FERC, and on May 24, 2019, OG&E filed a FERC 206 complaint against SPP, alleging that SPP's forced unwinding of the revenue credit payments to OG&E would violate the provisions of the Sponsored Upgrade Agreement and of the applicable tariff. OG&E's filing requested that the FERC rule that SPP is not entitled to seek refunds or in any other way seek to unwind the revenue credit payments it had paid to OG&E pursuant to the Sponsored Upgrade Agreement. SPP's response to OG&E's filing agreed that OG&E should be entitled to keep its Z2 payments and argued that SPP should not be held responsible for those payments if refunds are ordered. Further, SPP has requested the FERC to negotiate a global settlement with all impacted parties, including other project sponsors who, like OG&E, have also filed complaints at FERC contending that the payments they have received cannot properly be unwound. On February 20, 2020, the FERC denied OG&E's request for rehearing of its February 28, 2019 order, denying the waiver and ruling that SPP must seek refunds from project sponsors for Z2 payments for the 2008 - 2015 period and pay them back to transmission owners. The FERC also denied SPP's request for a stay and for institution of settlement procedures. The FERC stated it would not institute settlement procedures unless parties on both sides of the matter requested them. The FERC did not rule on OG&E's complaint or the complaints of other project sponsors, or consider SPP's refund plan. The FERC thus has not set any date for payment of refunds. The FERC's order denying the waiver and requiring refunds is now appealable, and OG&E intends to file a timely appeal. OG&E cannot predict the outcome of this proceeding based on currently available information, and as of December 31, 2019 and at present time, OG&E has not reserved an amount for a potential refund. If the reversal of the July 2016 FERC order remains intact, OG&E estimates it would be required to refund $13.0 million, which is net of amounts paid to other utilities for upgrades and would be subject to interest at the FERC-approved rate. If refunds were required, recovery of these upgrade credits would shift to future periods. Of the $13.0 million, OG&E would be impacted by $5.0 million in expense that initially benefited OG&E in 2016, and OG&E customers would incur a net impact of $8.0 million in expense through rider mechanisms or the FERC formula rate. SPP has recently proposed eliminating Attachment Z2 revenue crediting and replacing it with a different mechanism that would provide project sponsors such as OG&E the same level of recovery they would receive if payments continued under Attachment Z2. The FERC rejected that proposal to the extent it would limit recovery to the amount of the upgrade sponsor's directly assigned upgrade costs with interest, finding that providing the possibility of recovering greater than the cost of the investment could serve as an incentive for entities to build merchant transmission projects. The SPP can resubmit a proposal without that cap. APSC - Environmental Compliance Plan Rider On May 31, 2019, OG&E filed an environmental compliance plan rider in Arkansas to recover its investment for the environmentally mandated costs associated with the Dry Scrubbers project and the conversion of Muskogee Units 4 and 5 to natural gas. The filing is an interim surcharge, subject to refund, that began with the first billing cycle of June 2019. OG&E is reserving the amounts collected through the interim surcharge, pending APSC approval of OG&E's filing. A hearing on the merits was held on December 17, 2019. The primary question before the APSC is whether a company can utilize an environmental compliance plan rider while also regulated under a formula rate plan. OG&E is awaiting a final decision from the APSC. Arkansas 2019 Formula Rate Plan Filing OG&E filed its second evaluation report under its Formula Rate Plan in October 2019. On January 29, 2020, OG&E, the General Staff of the APSC and the Office of the Arkansas Attorney General filed a settlement agreement requesting the APSC approve a $5.2 million revenue increase, with rates effective April 1, 2020. The settling parties agreed that the Series I grid modernization projects are prudent in both action and cost and that the Series II grid modernization projects are prudent in action only and the determination of prudence of costs will be reserved until the actual historical costs are reviewed. The settling parties also agreed that OG&E will no longer use projections for the remaining initial term or extension of its current Formula Rate Plan and that all costs will be included for recovery for the first time in the historical year. A hearing was held on February 5, 2020, and OG&E is awaiting a final decision from the APSC. Oklahoma Grid Enhancement Plan On February 24, 2020, OG&E filed an application with the OCC for approval of a mechanism that allows for interim recovery of the costs associated with its grid enhancement plan. The plan includes approximately $800 million of strategic, data-driven investments, over five years, covering grid resiliency, grid automation, communication systems and technology platforms and applications. A procedural schedule has not been set by the OCC. Oklahoma Retail Electric Supplier Certified Territory Act Causes Certain rural electric cooperative electricity suppliers have filed complaints with the OCC alleging that OG&E has violated the Oklahoma Retail Electric Supplier Certified Territory Act. OG&E believes it is lawfully serving customers specifically exempted from this act and has presented evidence and testimony to the OCC supporting its position. If the OCC were to ultimately find that some or all of the customers being served are not exempted, then OG&E would have to evaluate the recoverability of some plant investment made to serve these customers. OG&E may also be required to reimburse certified territory suppliers for an amount of lost revenue.

Quarterly Financial Data

Quarterly Financial Data	9 Months Ended
	Sep. 30, 2019
Quarterly Financial Data [Abstract]
Quarterly Financial Information [Text Block]	Quarterly Financial Data (Unaudited) Due to the seasonal fluctuations and other factors of OG&E's business, the operating results for interim periods are not necessarily indicative of the results that may be expected for the year. In OG&E's opinion, the following quarterly financial data includes all adjustments, consisting of normal recurring adjustments, necessary to fairly present such amounts. Summarized quarterly unaudited financial data is as follows: Quarter Ended ( In millions) March 31 June 30 September 30 December 31 Total Operating revenues 2019 $ 490.0 $ 513.7 $ 755.4 $ 472.5 $ 2,231.6 2018 $ 492.7 $ 567.0 $ 698.8 $ 511.8 $ 2,270.3 Operating income 2019 $ 50.3 $ 110.6 $ 275.0 $ 71.8 $ 507.7 2018 $ 67.1 $ 138.3 $ 230.3 $ 58.5 $ 494.2 Net income 2019 $ 19.6 $ 74.5 $ 227.2 $ 28.9 $ 350.2 2018 $ 31.3 $ 92.0 $ 183.9 $ 20.8 $ 328.0

Schedule II

Schedule II	9 Months Ended
	Sep. 30, 2019
Schedule II [Abstract]
SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	OKLAHOMA GAS AND ELECTRIC COMPANY SCHEDULE II - Valuation and Qualifying Accounts Additions Description Balance at Beginning of Period Charged to Costs and Expenses Deductions (A) Balance at End of Period (In millions) Balance at December 31, 2017 Reserve for Uncollectible Accounts $ 1.5 $ 2.6 $ 2.6 $ 1.5 Balance at December 31, 2018 Reserve for Uncollectible Accounts $ 1.5 $ 3.4 $ 3.2 $ 1.7 Balance at December 31, 2019 Reserve for Uncollectible Accounts $ 1.7 $ 2.2 $ 2.4 $ 1.5

Leases, Codification Topic 842

Leases, Codification Topic 842	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure	Leases Based on its evaluation of all contracts under ASC 842, as described in Note 1, OG&E concluded it has operating lease obligations for railcar leases and wind farm land leases. Operating Leases OG&E Railcar Lease Agreement Effective February 1, 2019, OG&E renewed a railcar lease agreement for 780 rotary gondola railcars to transport coal from Wyoming to OG&E's coal-fired generation units. Rental payments are charged to fuel expense and are recovered through OG&E's fuel adjustment clauses. On February 1, 2024, OG&E has the option to either purchase the railcars at a stipulated fair market value or renew the lease. If OG&E chooses not to purchase the railcars or renew the lease agreement and the actual fair value of the railcars is less than the stipulated fair market value, OG&E would be responsible for the difference in those values up to a maximum of $6.8 million. OG&E Wind Farm Land Lease Agreements OG&E has operating leases related to land for OG&E's Centennial, OU Spirit and Crossroads wind farms with terms of 25 to 30 years. The Centennial lease has rent escalations which increase annually based on the Consumer Price Index. While lease liabilities are not remeasured as a result of changes to the Consumer Price Index, changes to the Consumer Price Index are treated as variable lease payments and recognized in the period in which the obligation for those payments was incurred. The OU Spirit and Crossroads leases have rent escalations which increase after five and 10 years. Although the leases are cancellable, OG&E is required to make annual lease payments as long as the wind turbines are located on the land. OG&E does not expect to terminate the leases until the wind turbines reach the end of their useful life. Financial Statement Information and Maturity Analysis of Lease Liabilities Operating lease cost was $5.1 million, $4.1 million and $5.4 million for the years ended December 31, 2019, 2018 and 2017, respectively. The following table presents amounts recognized for operating leases in OG&E's 2019 Cash Flow Statement and Balance Sheet and supplemental information related to those amounts recognized, as well as a maturity analysis of OG&E's operating lease liabilities. (In millions) Year Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 4.8 Right-of-use assets obtained in exchange for new operating lease liabilities $ 10.7 (Dollars in millions) December 31, 2019 Right-of-use assets at period end (A) $ 39.6 Operating lease liabilities at period end (B) $ 44.3 Operating lease weighted-average remaining lease term (in years) 13.5 Operating lease weighted-average discount rate 3.9 % December 31, Future minimum operating lease payments as of: 2019 2018(C)(D) (In millions) 2019 $ — $ 21.1 2020 5.3 2.9 2021 5.2 2.9 2022 5.2 2.9 2023 5.2 2.9 2024 3.1 3.0 Thereafter 34.7 34.6 Total future minimum lease payments 58.7 $ 70.3 Less: Imputed interest 14.4 Present value of net minimum lease payments $ 44.3 (A) Included in Property, Plant and Equipment in the 2019 Balance Sheet. (B) Included in Other Deferred Credits and Other Liabilities in the 2019 Balance Sheet. (C) Amounts included for comparability and accounted for in accordance with ASC 840, "Leases."

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reclassifications [Text Block]		ReclassificationsCertain prior year amounts have been reclassified to conform to the current year presentation.
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]		Summary of Significant Accounting Policies Organization OG&E generates, transmits, distributes and sells electric energy in Oklahoma and western Arkansas. Its operations are subject to regulation by the OCC, the APSC and the FERC. OG&E was incorporated in 1902 under the laws of the Oklahoma Territory. OG&E is the largest electric utility in Oklahoma, and its franchised service territory includes Fort Smith, Arkansas and the surrounding communities. OG&E sold its retail natural gas business in 1928 and is no longer engaged in the natural gas distribution business. OG&E is a wholly-owned subsidiary of OGE Energy, a holding company with investments in energy and energy services providers offering physical delivery and related services for both electricity and natural gas primarily in the south central U.S. Cash and Cash Equivalents Allowance for Uncollectible Accounts Receivable Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off. To the extent the historical collection rates are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the Balance Sheets and is included in Other Operation and Maintenance Expense in the Statements of Income. The allowance for uncollectible accounts receivable was $1.5 million and $1.7 million at December 31, 2019 and 2018, respectively. New business customers are required to provide a security deposit in the form of cash, bond or irrevocable letter of credit that is refunded when the account is closed. New residential customers whose outside credit scores indicate an elevated risk are required to provide a security deposit that is refunded based on customer protection rules defined by the OCC and the Depreciation and Amortization The provision for depreciation, which was 2.7 percent of the average depreciable utility plant for both 2019 and 2018, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2020, the provision for depreciation is projected to be 2.7 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2019, 98.9 percent will be amortized over 10.4 years with the remaining 1.1 percent of the intangible plant balance at December 31, 2019 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life and $3.3 million for certain transmission substation facilities in OG&E's service territory, which are being amortized over a 37 to 59 year period. Allowance for Funds Used During Construction Allowance for funds used during construction, a non-cash item, is reflected as an increase to Net Other Income and a reduction to Interest Expense in the Statements of Income and as an increase to Construction Work in Progress in the Balance Sheets. Allowance for funds used during construction is calculated according to the FERC requirements for the imputed cost of equity and borrowed funds. Allowance for funds used during construction rates, compounded semi-annually, were 7.6 percent, 7.6 percent and 8.2 percent for the years ended December 31, 2019, 2018 and 2017, respectively. Collection of Sales Tax In the normal course of its operations, OG&E collects sales tax from its customers. OG&E records a current liability for sales taxes when it bills its customers and eliminates this liability when the taxes are remitted to the appropriate governmental authorities. OG&E excludes the sales tax collected from its operating revenues. Revenue Recognition General OG&E recognizes revenue from electric sales when power is delivered to customers. The performance obligation to deliver electricity is generally created and satisfied simultaneously, and the provisions of the regulatory-approved tariff determine the charges OG&E may bill the customer, payment due date and other pertinent rights and obligations of both parties. OG&E reads its customers' meters and sends bills to its customers throughout each month. As a result, there is a significant amount of customers' electricity consumption that has not been billed at the end of each month. OG&E accrues an estimate of the revenues for electric sales delivered since the latest billings. Unbilled revenue is presented in Accrued Unbilled Revenues in the Balance Sheets and in Revenues from Contracts with Customers in the Statements of Income based on estimates of usage and prices during the period. The estimates that management uses in this calculation could vary from the actual amounts to be paid by customers. Integrated Market and Transmission OG&E currently owns and operates transmission and generation facilities as part of a vertically integrated utility. OG&E is a member of the SPP regional transmission organization and has transferred operational authority, but not ownership, of OG&E's transmission facilities to the SPP. The SPP has implemented FERC-approved regional day-ahead and real-time markets for energy and operating services, as well as associated transmission congestion rights. Collectively the three markets operate together under the global name, SPP Integrated Marketplace. OG&E represents owned and contracted generation assets and customer load in the SPP Integrated Marketplace for the sole benefit of its customers. OG&E has not participated in the SPP Integrated Marketplace for any speculative trading activities. OG&E records the SPP Integrated Marketplace transactions as sales or purchases per FERC Order 668, which requires that purchases and sales be recorded on a net basis for each settlement period of the SPP Integrated Marketplace. Purchases and sales are based on the fixed transaction price determined by the market at the time of the purchase or sale and the MWh quantity purchased or sold. These results are reported as Revenues from Contracts with Customers or Cost of Sales in the Financial Statements. OG&E revenues, expenses, assets and liabilities may be adversely affected by changes in the organization, operating and regulation by the FERC or the SPP. OG&E's transmission revenues are generated by the use of OG&E's transmission network by the SPP, which operates the network, on behalf of other transmission owners. OG&E recognizes revenue on the sale of transmission service to its customers over time as the service is provided in the amount OG&E has a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by OG&E's FERC-approved formula transmission rates along with other SPP-specific charges and the megawatt quantity reserved. Other Revenues Revenues from Alternative Revenue Programs Other Revenues in the Statements of Income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either program type have been completed, OG&E recognizes the additional revenues if (i) the program is established by an order from OG&E's regulatory commission that allows for automatic adjustment of future rates; (ii) the amount of additional revenues for the period is objectively determinable and is probable of recovery; and (iii) the additional revenues will be collected within 24 months following the end of the annual period in which they are recognized. Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC. Leases OG&E evaluates all contracts under ASC 842 to determine if the contract is or contains a lease and to determine classification as an operating or finance lease. If a lease is identified, OG&E recognizes a right-of-use asset and a lease liability in its Balance Sheets. OG&E recognizes and measures a lease liability when it concludes the contract contains an identified asset that OG&E controls through having the right to obtain substantially all of the economic benefits and the right to direct the use of the identified asset. The liability is equal to the present value of lease payments, and the asset is based on the liability, subject to adjustment, such as for initial direct costs. Further, OG&E utilizes an incremental borrowing rate for purposes of measuring lease liabilities, if the discount rate is not implicit in the lease. To calculate the incremental borrowing rate, OG&E starts with a current pricing report for OG&E's senior unsecured notes, which indicates rates for periods reflective of the lease term, and adjusts for the effects of collateral to arrive at the secured incremental borrowing rate. As permitted by ASC 842, OG&E made an accounting policy election to not apply the balance sheet recognition requirements to short-term leases and to not separate lease components from nonlease components when recognizing and measuring lease liabilities. For income statement purposes, OG&E records operating lease expense on a straight-line basis. Accrued Vacation OG&E accrues vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.
Public Utilities, Policy [Policy Text Block]		Accounting Records The accounting records of OG&E are maintained in accordance with the Uniform System of Accounts prescribed by the FERC and adopted by the OCC and the APSC. Additionally, OG&E, as a regulated utility, is subject to accounting principles for certain types of rate-regulated activities, which provide that certain incurred costs that would otherwise be charged to expense can be deferred as regulatory assets, based on the expected recovery from customers in future rates. Likewise, certain actual or anticipated credits that would otherwise reduce expense can be deferred as regulatory liabilities, based on the expected flowback to customers in future rates. Management's expected recovery of deferred costs and flowback of deferred credits generally results from specific decisions by regulators granting such ratemaking treatment.
Use of Estimates, Policy [Policy Text Block]		Use of EstimatesIn preparing the Financial Statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Changes to these assumptions and estimates could have a material effect on OG&E's Financial Statements. However, OG&E believes it has taken reasonable positions where assumptions and estimates are used in order to minimize the negative financial impact to OG&E that could result if actual results vary from the assumptions and estimates. In management's opinion, the areas of OG&E where the most significant judgment is exercised include the determination of Pension Plan assumptions, income taxes, contingency reserves, asset retirement obligations, depreciable lives of property, plant and equipment, regulatory assets and liabilities and unbilled revenues.
Cash and Cash Equivalents, Policy [Policy Text Block]		Cash and Cash Equivalents
Allowance for Doubtful Accounts, Policy [Policy Text Block]		Allowance for Uncollectible Accounts Receivable Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off. To the extent the historical collection rates are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the Balance Sheets and is included in Other Operation and Maintenance Expense in the Statements of Income. The allowance for uncollectible accounts receivable was $1.5 million and $1.7 million at December 31, 2019 and 2018, respectively. New business customers are required to provide a security deposit in the form of cash, bond or irrevocable letter of credit that is refunded when the account is closed. New residential customers whose outside credit scores indicate an elevated risk are required to provide a security deposit that is refunded based on customer protection rules defined by the OCC and the
Inventory, Policy [Policy Text Block]		Fuel Inventories Fuel inventories for the generation of electricity consist of coal, natural gas and oil. OG&E uses the weighted-average cost method of accounting for inventory that is physically added to or withdrawn from storage or stockpiles. The amount of fuel inventory was $46.3 million and $57.6 million at December 31, 2019 and 2018, respectively.
Property, Plant and Equipment, Policy [Policy Text Block]		Property, Plant and Equipment
Depreciation and Amortization, Policy [Policy Text Block]		Depreciation and Amortization The provision for depreciation, which was 2.7 percent of the average depreciable utility plant for both 2019 and 2018, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2020, the provision for depreciation is projected to be 2.7 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2019, 98.9 percent will be amortized over 10.4 years with the remaining 1.1 percent of the intangible plant balance at December 31, 2019 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life and $3.3 million for certain transmission substation facilities in OG&E's service territory, which are being amortized over a 37 to 59 year period.
Asset Retirement Obligation [Policy Text Block]		Asset Retirement ObligationsOG&E has asset retirement obligations primarily associated with the removal of company-owned wind turbines on leased land, as well as the removal of asbestos from certain power generating stations. OG&E has recorded asset retirement obligations that are being accreted over their respective lives ranging from ten to 68 years.
Allowance for Funds Used During Construction, Policy [Policy Text Block]		Allowance for Funds Used During Construction
Collection of Sales Tax, Policy [Policy Text Block]		Collection of Sales Tax
Revenue Recognition, Policy [Policy Text Block]	Statements of Income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either program type have been completed, OG&E recognizes the additional revenues if (i) the program is established by an order from OG&E's regulatory commission that allows for automatic adjustment of future rates; (ii) the amount of additional revenues for the period is objectively determinable and is probable of recovery; and (iii) the additional revenues will be collected within 24 months following the end of the annual period in which they are recognized.
Fuel Adjustment Clauses, Policy [Policy Text Block]		Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC.
Lessee, Leases		LeasesOG&E evaluates all contracts under ASC 842 to determine if the contract is or contains a lease and to determine classification as an operating or finance lease. If a lease is identified, OG&E recognizes a right-of-use asset and a lease liability in its Balance Sheets. OG&E recognizes and measures a lease liability when it concludes the contract contains an identified asset that OG&E controls through having the right to obtain substantially all of the economic benefits and the right to direct the use of the identified asset. The liability is equal to the present value of lease payments, and the asset is based on the liability, subject to adjustment, such as for initial direct costs. Further, OG&E utilizes an incremental borrowing rate for purposes of measuring lease liabilities, if the discount rate is not implicit in the lease. To calculate the incremental borrowing rate, OG&E starts with a current pricing report for OG&E's senior unsecured notes, which indicates rates for periods reflective of the lease term, and adjusts for the effects of collateral to arrive at the secured incremental borrowing rate. As permitted by ASC 842, OG&E made an accounting policy election to not apply the balance sheet recognition requirements to short-term leases and to not separate lease components from nonlease components when recognizing and measuring lease liabilities. For income statement purposes, OG&E records operating lease expense on a straight-line basis.
Income Taxes, Policy [Policy Text Block]		Income TaxesOG&E is a member of an affiliated group that files consolidated income tax returns in the U.S. federal jurisdiction and various state jurisdictions. Income taxes are generally allocated to each company in the affiliated group based on its stand-alone taxable income or loss. Federal investment tax credits previously claimed on electric utility property have been deferred and will be amortized to income over the life of the related property. OG&E uses the asset and liability method of accounting for income taxes. Under this method, a deferred tax asset or liability is recognized for the estimated future tax effects attributable to temporary differences between the financial statement basis and the tax basis of assets and liabilities as well as tax credit carry forwards and net operating loss carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period of the change. OG&E recognizes interest related to unrecognized tax benefits in Interest Expense and recognizes penalties in Other Expense in the Statements of Income.
Accrued Vacation, Policy [Policy Text Block]		Accrued Vacation OG&E accrues vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.
Environmental Costs, Policy [Policy Text Block]		Accruals for environmental costs are recognized when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. Costs are charged to expense or deferred as a regulatory asset based on expected recovery from customers in future rates, if they relate to the remediation of conditions caused by past operations or if they are not expected to mitigate or prevent contamination from future operations. Where environmental expenditures relate to facilities currently in use, such as pollution control equipment, the costs may be capitalized and depreciated over the future service periods. Estimated remediation costs are recorded at undiscounted amounts, independent of any insurance or rate recovery, based on prior experience, assessments and current technology. Accrued obligations are regularly adjusted as environmental assessments and estimates are revised and remediation efforts proceed. For sites where OG&E has been designated as one of several potentially responsible parties, the amount accrued represents OG&E's estimated share of the cost. OG&E had $18.7 million and $23.4 million in accrued environmental liabilities at December 31, 2019 and 2018, respectively, which are included in OG&E's asset retirement obligations.
Related Party Transactions [Policy Text Block]	OGE Energy charges operating costs to OG&E based on several factors. Operating costs directly related to OG&E are assigned as such. Operating costs incurred for the benefit of OG&E are allocated either as overhead based primarily on labor costs or using the "Distrigas" method.
Fair Value of Financial Instruments, Policy [Policy Text Block]		Fair Value Measurements The classification of OG&E's fair value measurements requires judgment regarding the degree to which market data is observable or corroborated by observable market data. GAAP establishes a fair value hierarchy that prioritizes the inputs used to measure fair value based on observable and unobservable data. The hierarchy categorizes the inputs into three levels, with the highest priority given to quoted prices in active markets for identical unrestricted assets or liabilities (Level 1) and the lowest priority given to unobservable inputs (Level 3). Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels defined in the fair value hierarchy are as follows: Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the reporting entity's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]		Performance Units Under the Stock Incentive Plan, OGE Energy has issued performance units which represent the value of one share of OGE Energy's common stock. The performance units provide for accelerated vesting if there is a change in control (as defined in the Stock Incentive Plan). Each performance unit is subject to forfeiture if the recipient terminates employment with OGE Energy or a subsidiary prior to the end of the primarily three-year award cycle for any reason other than death, disability or retirement. In the event of death, disability or retirement, a participant will receive a prorated payment based on such participant's number of full months of service during the award cycle, further adjusted based on the achievement of the performance goals during the award cycle. OG&E estimates expected forfeitures in accounting for performance unit compensation expense. The performance units granted based on total shareholder return are contingently awarded and will be payable in shares of OGE Energy's common stock subject to the condition that the number of performance units, if any, earned by the employees upon the expiration of a primarily three-year award cycle (i.e., three-year cliff vesting period) is dependent on OGE Energy's total shareholder return ranking relative to a peer group of companies. The performance units granted based on earnings per share are contingently awarded and will be payable in shares of OGE Energy's common stock based on OGE Energy's earnings per share growth over a primarily three-year award cycle (i.e., three-year cliff vesting period) compared to a target set at the time of the grant by the Compensation Committee of OGE Energy's Board of Directors. All of these performance units are classified as equity in OGE Energy's Consolidated Balance Sheets. If there is no or only a partial payout for the performance units at the end of the award cycle, the unearned performance units are cancelled. Payout requires approval of the Compensation Committee of OGE Energy's Board of Directors. Payouts, if any, are all made in common stock and are considered made when the payout is approved by the Compensation Committee. Performance Units – Earnings Per Share Restricted Stock Units Under the Stock Incentive Plan, OGE Energy has issued restricted stock units to certain existing non-officer employees as well as other executives upon hire to attract and retain individuals to be competitive in the marketplace, and for the 2019 grant cycle, restricted stock units were granted in lieu of performance units based on earnings per share. The restricted stock units vest primarily in a three-year award cycle (i.e., three-year cliff vesting period). Prior to vesting, each restricted stock unit is subject to forfeiture if the recipient ceases to render substantial services to OGE Energy or a subsidiary. These restricted stock units may not be sold, assigned, transferred or pledged and are subject to a risk of forfeiture. The fair value of the restricted stock units was based on the closing market price of OGE Energy's common stock on the grant date. Compensation expense for the restricted stock units is a fixed amount determined at the grant date fair value and is recognized as services are rendered by employees over a primarily three-year vesting period. Also, for those restricted stock units that vest in one-third annual increments over a three-year cycle, OG&E treats its restricted stock units as multiple separate awards by recording compensation expense separately for each tranche whereby a substantial portion of the expense is recognized in the earlier years in the requisite service period.
Pension and Other Postretirement Plans, Policy [Policy Text Block]	As defined in the fair value hierarchy, Level 1 inputs are quoted prices in active markets for identical unrestricted assets or liabilities that are accessible by the Pension Plan at the measurement date. Level 2 inputs are inputs other than quoted prices in active markets included within Level 1 that are either directly or indirectly observable at the reporting date for the asset or liability for substantially the full term of the asset or liability. Level 2 inputs include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3 inputs are prices or valuation techniques for the asset or liability that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Unobservable inputs reflect the Plan's own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).	Pension Plan and Restoration of Retirement Income Plan OG&E's employees participate in OGE Energy's Pension Plan and Restoration of Retirement Income Plan. It is OGE Energy's policy to fund the Pension Plan on a current basis based on the net periodic pension expense as determined by OGE Energy's actuarial consultants. Such contributions are intended to provide not only for benefits attributed to service to date but also for those expected to be earned in the future. OGE Energy made a $20.0 million and $15.0 million contribution to its Pension Plan in 2019 and 2018, of which $5.0 million is related to OG&E in both 2019 and 2018. OGE Energy has not determined whether it will need to make any contributions to the Pension Plan in 2020. Any contribution to the Pension Plan during 2020 would be a discretionary contribution, anticipated to be in the form of cash, and is not required to satisfy the minimum regulatory funding requirement specified by the Employee Retirement Income Security Act of 1974, as amended. OGE Energy could be required to make additional contributions if the value of its pension trust and postretirement benefit plan trust assets are adversely impacted by a major market disruption in the future. In accordance with ASC Topic 715, "Compensation - Retirement Benefits," a one-time settlement charge is required to be recorded by an organization when lump sum payments or other settlements that relieve the organization from the responsibility for the pension benefit obligation during the plan year exceed the service cost and interest cost components of the organization's net periodic pension cost. During 2019, 2018 and 2017, OG&E experienced an increase in both the number of employees electing to retire and the amount of lump sum payments paid to such employees upon retirement, which resulted in OG&E recording pension plan settlement charges as presented in the net periodic benefit cost table below. The pension settlement charges did not require a cash outlay by OG&E and did not increase OG&E's total pension expense over time, as the charges were an acceleration of costs that otherwise would be recognized as pension expense in future periods. OGE Energy provides a Restoration of Retirement Income Plan to those participants in OGE Energy's Pension Plan whose benefits are subject to certain limitations of the Code. Participants in the Restoration of Retirement Income Plan receive the same benefits that they would have received under OGE Energy's Pension Plan in the absence of limitations imposed by the federal tax laws. The Restoration of Retirement Income Plan is intended to be an unfunded plan. Postretirement Benefit Plans In addition to providing pension benefits, OGE Energy provides certain medical and life insurance benefits for eligible retired members. Regular, full-time, active employees hired prior to February 1, 2000 whose age and years of credited service total or exceed 80 or have attained at least age 55 with 10 or more years of service at the time of retirement are entitled to postretirement medical benefits, while employees hired on or after February 1, 2000 are not entitled to postretirement medical benefits. Eligible retirees must contribute such amount as OGE Energy specifies from time to time toward the cost of coverage for postretirement benefits. The benefits are subject to deductibles, co-payment provisions and other limitations. OG&E charges postretirement benefit costs to expense and includes an annual amount as a component of the cost-of-service in future ratemaking proceedings.
Plan Investments, Policies and Strategies, Policy [Policy Text Block]		Pension Plan Investments, Policies and Strategies The Pension Plan assets are held in a trust which follows an investment policy and strategy designed to reduce the funded status volatility of the Plan by utilizing liability driven investing. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The investment policy follows a glide path approach that shifts a higher portfolio weighting to fixed income as the Plan's funded status increases. The table below sets forth the targeted fixed income and equity allocations at different funded status levels. Projected Benefit Obligation Funded Status Thresholds <90% 95% 100% 105% 110% 115% 120% Fixed income 50% 58% 65% 73% 80% 85% 90% Equity 50% 42% 35% 27% 20% 15% 10% Total 100% 100% 100% 100% 100% 100% 100% Within the portfolio's overall allocation to equities, the funds are allocated according to the guidelines in the table below. Asset Class Target Allocation Minimum Maximum Domestic Large Cap Equity 40% 35% 60% Domestic Mid-Cap Equity 15% 5% 25% Domestic Small-Cap Equity 25% 5% 30% International Equity 20% 10% 30% OGE Energy has retained an investment consultant responsible for the general investment oversight, analysis, monitoring investment guideline compliance and providing quarterly reports to certain of OG&E's members and OGE Energy's Investment Committee. The various investment managers used by the trust operate within the general operating objectives as established in the investment policy and within the specific guidelines established for each investment manager's respective portfolio. The portfolio is rebalanced at least on an annual basis to bring the asset allocations of various managers in line with the target asset allocation listed above. More frequent rebalancing may occur if there are dramatic price movements in the financial markets which may cause the trust's exposure to any asset class to exceed or fall below the established allowable guidelines. To evaluate the progress of the portfolio, investment performance is reviewed quarterly. It is, however, expected that performance goals will be met over a full market cycle, normally defined as a three to five year period. Analysis of performance is within the context of the prevailing investment environment and the advisors' investment style. The goal of the trust is to provide a rate of return consistently from three percent to five percent over the rate of inflation (as measured by the national Consumer Price Index) on a fee adjusted basis over a typical market cycle of no less than three years and no more than five years. Each investment manager is expected to outperform its respective benchmark. Below is a list of each asset class utilized with appropriate comparative benchmark(s) each manager is evaluated against: Asset Class Comparative Benchmark(s) Active Duration Fixed Income Bloomberg Barclays Aggregate Long Duration Fixed Income Duration blended Barclays Long Government/Credit & Barclays Universal Equity Index Standard & Poor's 500 Index Mid-Cap Equity Russell Midcap Index Russell Midcap Value Index Small-Cap Equity Russell 2000 Index Russell 2000 Value Index International Equity Morgan Stanley Capital International ACWI ex-U.S. The fixed income managers are expected to use discretion over the asset mix of the trust assets in their efforts to maximize risk-adjusted performance. Exposure to any single issuer, other than the U.S. government, its agencies or its instrumentalities (which have no limits), is limited to five percent of the fixed income portfolio as measured by market value. At least 75 percent of the invested assets must possess an investment-grade rating at or above Baa3 or BBB- by Moody's Investors Service, S&P's Global Ratings or Fitch Ratings. The portfolio may invest up to 10 percent of the portfolio's market value in convertible bonds as long as the securities purchased meet the quality guidelines. A portfolio may invest up to 15 percent of the portfolio's market value in private placement, including 144A securities with or without registration rights and allow for futures to be traded in the portfolio. The purchase of any of OGE Energy's equity, debt or other securities is prohibited. The domestic value equity managers focus on stocks that the manager believes are undervalued in price and earn an average or less than average return on assets and often pays out higher than average dividend payments. The domestic growth equity manager will invest primarily in growth companies which consistently experience above average growth in earnings and sales, earn a high return on assets and reinvest cash flow into existing business. The domestic mid-cap equity portfolio manager focuses on companies with market capitalizations lower than the average company traded on the public exchanges with the following characteristics: price/earnings ratio at or near the Russell Midcap Index, small dividend yield, return on equity at or near the Russell Midcap Index and an earnings per share growth rate at or near the Russell Midcap Index. The domestic small-cap equity manager will purchase shares of companies with market capitalizations lower than the average company traded on the public exchanges with the following characteristics: price/earnings ratio at or near the Russell 2000, small dividend yield, return on equity at or near the Russell 2000 and an earnings per share growth rate at or near the Russell 2000. The international global equity manager invests primarily in non-dollar denominated equity securities. Investing internationally diversifies the overall trust across the global equity markets. The manager is required to operate under certain restrictions including regional constraints, diversification requirements and percentage of U.S. securities. The Morgan Stanley Capital International All Country World ex-U.S. Index is the benchmark for comparative performance purposes. The Morgan Stanley Capital International All Country World ex-U.S. Index is a market value weighted index designed to measure the combined equity market performance of developed and emerging markets countries, excluding the U.S. All of the equities which are purchased for the international portfolio are thoroughly researched. All securities are freely traded on a recognized stock exchange, and there are no over-the-counter derivatives. The following investment categories are excluded: options (other than traded currency options), commodities, futures (other than currency futures or currency hedging), short sales/margin purchases, private placements, unlisted securities and real estate (but not real estate shares). For all domestic equity investment managers, no more than five percent can be invested in any one stock at the time of purchase and no more than 10 percent after accounting for price appreciation. Options or financial futures may not be purchased unless prior approval of OGE Energy's Investment Committee is received. The purchase of securities on margin is prohibited as is securities lending. Private placement or venture capital may not be purchased. All interest and dividend payments must be swept on a daily basis into a short-term money market fund for re-deployment. The purchase of any of OGE Energy's equity, debt or other securities is prohibited. The purchase of equity or debt issues of the portfolio manager's organization is also prohibited. The aggregate positions in any company may not exceed one percent of the fair market value of its outstanding stock.
Postemployment Benefit Plans, Policy [Policy Text Block]	Post-Employment Benefit Plan Disabled employees receiving benefits from OGE Energy's Group Long-Term Disability Plan are entitled to continue participating in OGE Energy's Medical Plan along with their dependents. The post-employment benefit obligation represents the actuarial present value of estimated future medical benefits that are attributed to employee service rendered prior to the date as of which such information is presented. The obligation also includes future medical benefits expected to be paid to current employees participating in OGE Energy's Group Long-Term Disability Plan and their dependents, as defined in OGE Energy's Medical Plan. The post-employment benefit obligation is determined by an actuary on a basis similar to the accumulated postretirement benefit obligation. The estimated future medical benefits are projected to grow with expected future medical cost trend rates and are discounted for interest at the discount rate and for the probability that the participant will discontinue receiving benefits from OGE Energy's Group Long-Term Disability Plan due to death, recovery from disability or eligibility for retiree medical benefits. OG&E's post-employment benefit obligation was $1.7 million at both December 31, 2019 and 2018.
Pension and Other Postretirement Plans, Nonpension Benefits, Policy [Policy Text Block]		401(k) Plan OGE Energy provides a 401(k) Plan, and each regular full-time employee of OGE Energy or a participating affiliate is eligible to participate in the 401(k) Plan immediately. All other employees of OGE Energy or a participating affiliate are eligible to become participants in the 401(k) Plan after completing one year of service as defined in the 401(k) Plan. Participants may contribute each pay period any whole percentage between two percent and 19 percent of their compensation, as defined in the 401(k) Plan, for that pay period. Participants who have reached age 50 before the close of a year are allowed to make additional contributions referred to as "Catch-Up Contributions," subject to certain limitations of the Code. Participants may designate, at their discretion, all or any portion of their contributions as: (i) a before-tax contribution under Section 401(k) of the Code subject to the limitations thereof, (ii) a contribution made on a non-Roth after-tax basis or (iii) a Roth contribution. The 401(k) Plan also includes an eligible automatic contribution arrangement and provides for a qualified default investment alternative consistent with the U.S. Department of Labor regulations. Participants may elect, in accordance with the 401(k) Plan procedures, to have their future salary deferral rate to be automatically increased annually on a date and in an amount as specified by the participant in such election. For employees hired or rehired on or after December 1, 2009, OGE Energy contributes to the 401(k) Plan, on behalf of each participant, 200 percent of the participant's contributions up to five percent of compensation. No OGE Energy contributions are made with respect to a participant's Catch-Up Contributions, rollover contributions or with respect to a participant's contributions based on overtime payments, pay-in-lieu of overtime for exempt personnel, special lump-sum recognition awards and lump-sum merit awards included in compensation for determining the amount of participant contributions. Once made, OGE Energy's contribution may be directed to any available investment option in the 401(k) Plan. OGE Energy match contributions vest over a three-year period. After two years of service, participants become 20 percent vested in their OGE Energy contribution account and become fully vested on completing three years of service. In addition, participants fully vest when they are eligible for normal or early retirement under the Pension Plan requirements, in the event of their termination due to death or permanent disability or upon attainment of age 65 while employed by OGE Energy or its affiliates. OG&E contributed $11.0 million, $9.8 million and $9.7 million in 2019, 2018 and 2017, respectively, to the 401(k) Plan. Deferred Compensation Plan OGE Energy provides a nonqualified deferred compensation plan which is intended to be an unfunded plan. The plan's primary purpose is to provide a tax-deferred capital accumulation vehicle for a select group of management, highly compensated employees and non-employee members of the Board of Directors of OGE Energy and to supplement such employees' 401(k) Plan contributions as well as offering this plan to be competitive in the marketplace. Eligible employees who enroll in the plan have the following deferral options: (i) eligible employees may elect to defer up to a maximum of 70 percent of base salary and 100 percent of annual bonus awards or (ii) eligible employees may elect a deferral percentage of base salary and bonus awards based on the deferral percentage elected for a year under the 401(k) Plan with such deferrals to start when maximum deferrals to the qualified 401(k) Plan have been made because of limitations in that plan. Eligible directors who enroll in the plan may elect to defer up to a maximum of 100 percent of directors' meeting fees and annual retainers. OGE Energy matches employee (but not non-employee director) deferrals to make up for any match lost in the 401(k) Plan because of deferrals to the deferred compensation plan and to allow for a match that would have been made under the 401(k) Plan on that portion of either the first six percent of total compensation or the first five percent of total compensation, depending on prior participant elections, deferred that exceeds the limits allowed in the 401(k) Plan. Matching credits vest based on years of service, with full vesting after three years or, if earlier, on retirement, disability, death, a change in control of OGE Energy or termination of the plan. Deferrals, plus any OGE Energy match, are credited to a recordkeeping account in the participant's name. Earnings on the deferrals are indexed to the assumed investment funds selected by the participant. In 2019, those investment options included an OGE Energy Common Stock fund, whose value was determined based on the stock price of OGE Energy's Common Stock.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies Organization (Policies)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Summary of Significant Accounting Policies Organization OG&E generates, transmits, distributes and sells electric energy in Oklahoma and western Arkansas. Its operations are subject to regulation by the OCC, the APSC and the FERC. OG&E was incorporated in 1902 under the laws of the Oklahoma Territory. OG&E is the largest electric utility in Oklahoma, and its franchised service territory includes Fort Smith, Arkansas and the surrounding communities. OG&E sold its retail natural gas business in 1928 and is no longer engaged in the natural gas distribution business. OG&E is a wholly-owned subsidiary of OGE Energy, a holding company with investments in energy and energy services providers offering physical delivery and related services for both electricity and natural gas primarily in the south central U.S. Cash and Cash Equivalents Allowance for Uncollectible Accounts Receivable Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off. To the extent the historical collection rates are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the Balance Sheets and is included in Other Operation and Maintenance Expense in the Statements of Income. The allowance for uncollectible accounts receivable was $1.5 million and $1.7 million at December 31, 2019 and 2018, respectively. New business customers are required to provide a security deposit in the form of cash, bond or irrevocable letter of credit that is refunded when the account is closed. New residential customers whose outside credit scores indicate an elevated risk are required to provide a security deposit that is refunded based on customer protection rules defined by the OCC and the Depreciation and Amortization The provision for depreciation, which was 2.7 percent of the average depreciable utility plant for both 2019 and 2018, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2020, the provision for depreciation is projected to be 2.7 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2019, 98.9 percent will be amortized over 10.4 years with the remaining 1.1 percent of the intangible plant balance at December 31, 2019 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life and $3.3 million for certain transmission substation facilities in OG&E's service territory, which are being amortized over a 37 to 59 year period. Allowance for Funds Used During Construction Allowance for funds used during construction, a non-cash item, is reflected as an increase to Net Other Income and a reduction to Interest Expense in the Statements of Income and as an increase to Construction Work in Progress in the Balance Sheets. Allowance for funds used during construction is calculated according to the FERC requirements for the imputed cost of equity and borrowed funds. Allowance for funds used during construction rates, compounded semi-annually, were 7.6 percent, 7.6 percent and 8.2 percent for the years ended December 31, 2019, 2018 and 2017, respectively. Collection of Sales Tax In the normal course of its operations, OG&E collects sales tax from its customers. OG&E records a current liability for sales taxes when it bills its customers and eliminates this liability when the taxes are remitted to the appropriate governmental authorities. OG&E excludes the sales tax collected from its operating revenues. Revenue Recognition General OG&E recognizes revenue from electric sales when power is delivered to customers. The performance obligation to deliver electricity is generally created and satisfied simultaneously, and the provisions of the regulatory-approved tariff determine the charges OG&E may bill the customer, payment due date and other pertinent rights and obligations of both parties. OG&E reads its customers' meters and sends bills to its customers throughout each month. As a result, there is a significant amount of customers' electricity consumption that has not been billed at the end of each month. OG&E accrues an estimate of the revenues for electric sales delivered since the latest billings. Unbilled revenue is presented in Accrued Unbilled Revenues in the Balance Sheets and in Revenues from Contracts with Customers in the Statements of Income based on estimates of usage and prices during the period. The estimates that management uses in this calculation could vary from the actual amounts to be paid by customers. Integrated Market and Transmission OG&E currently owns and operates transmission and generation facilities as part of a vertically integrated utility. OG&E is a member of the SPP regional transmission organization and has transferred operational authority, but not ownership, of OG&E's transmission facilities to the SPP. The SPP has implemented FERC-approved regional day-ahead and real-time markets for energy and operating services, as well as associated transmission congestion rights. Collectively the three markets operate together under the global name, SPP Integrated Marketplace. OG&E represents owned and contracted generation assets and customer load in the SPP Integrated Marketplace for the sole benefit of its customers. OG&E has not participated in the SPP Integrated Marketplace for any speculative trading activities. OG&E records the SPP Integrated Marketplace transactions as sales or purchases per FERC Order 668, which requires that purchases and sales be recorded on a net basis for each settlement period of the SPP Integrated Marketplace. Purchases and sales are based on the fixed transaction price determined by the market at the time of the purchase or sale and the MWh quantity purchased or sold. These results are reported as Revenues from Contracts with Customers or Cost of Sales in the Financial Statements. OG&E revenues, expenses, assets and liabilities may be adversely affected by changes in the organization, operating and regulation by the FERC or the SPP. OG&E's transmission revenues are generated by the use of OG&E's transmission network by the SPP, which operates the network, on behalf of other transmission owners. OG&E recognizes revenue on the sale of transmission service to its customers over time as the service is provided in the amount OG&E has a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by OG&E's FERC-approved formula transmission rates along with other SPP-specific charges and the megawatt quantity reserved. Other Revenues Revenues from Alternative Revenue Programs Other Revenues in the Statements of Income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either program type have been completed, OG&E recognizes the additional revenues if (i) the program is established by an order from OG&E's regulatory commission that allows for automatic adjustment of future rates; (ii) the amount of additional revenues for the period is objectively determinable and is probable of recovery; and (iii) the additional revenues will be collected within 24 months following the end of the annual period in which they are recognized. Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC. Leases OG&E evaluates all contracts under ASC 842 to determine if the contract is or contains a lease and to determine classification as an operating or finance lease. If a lease is identified, OG&E recognizes a right-of-use asset and a lease liability in its Balance Sheets. OG&E recognizes and measures a lease liability when it concludes the contract contains an identified asset that OG&E controls through having the right to obtain substantially all of the economic benefits and the right to direct the use of the identified asset. The liability is equal to the present value of lease payments, and the asset is based on the liability, subject to adjustment, such as for initial direct costs. Further, OG&E utilizes an incremental borrowing rate for purposes of measuring lease liabilities, if the discount rate is not implicit in the lease. To calculate the incremental borrowing rate, OG&E starts with a current pricing report for OG&E's senior unsecured notes, which indicates rates for periods reflective of the lease term, and adjusts for the effects of collateral to arrive at the secured incremental borrowing rate. As permitted by ASC 842, OG&E made an accounting policy election to not apply the balance sheet recognition requirements to short-term leases and to not separate lease components from nonlease components when recognizing and measuring lease liabilities. For income statement purposes, OG&E records operating lease expense on a straight-line basis. Accrued Vacation OG&E accrues vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies Use of Estimates (Policies)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Summary of Significant Accounting Policies Organization OG&E generates, transmits, distributes and sells electric energy in Oklahoma and western Arkansas. Its operations are subject to regulation by the OCC, the APSC and the FERC. OG&E was incorporated in 1902 under the laws of the Oklahoma Territory. OG&E is the largest electric utility in Oklahoma, and its franchised service territory includes Fort Smith, Arkansas and the surrounding communities. OG&E sold its retail natural gas business in 1928 and is no longer engaged in the natural gas distribution business. OG&E is a wholly-owned subsidiary of OGE Energy, a holding company with investments in energy and energy services providers offering physical delivery and related services for both electricity and natural gas primarily in the south central U.S. Cash and Cash Equivalents Allowance for Uncollectible Accounts Receivable Customer balances are generally written off if not collected within six months after the final billing date. The allowance for uncollectible accounts receivable for OG&E is calculated by multiplying the last six months of electric revenue by the provision rate, which is based on a 12-month historical average of actual balances written off. To the extent the historical collection rates are not representative of future collections, there could be an effect on the amount of uncollectible expense recognized. Also, a portion of the uncollectible provision related to fuel within the Oklahoma jurisdiction is being recovered through the fuel adjustment clause. The allowance for uncollectible accounts receivable is a reduction to Accounts Receivable in the Balance Sheets and is included in Other Operation and Maintenance Expense in the Statements of Income. The allowance for uncollectible accounts receivable was $1.5 million and $1.7 million at December 31, 2019 and 2018, respectively. New business customers are required to provide a security deposit in the form of cash, bond or irrevocable letter of credit that is refunded when the account is closed. New residential customers whose outside credit scores indicate an elevated risk are required to provide a security deposit that is refunded based on customer protection rules defined by the OCC and the Depreciation and Amortization The provision for depreciation, which was 2.7 percent of the average depreciable utility plant for both 2019 and 2018, is calculated using the straight-line method over the estimated service life of the utility assets. Depreciation is provided at the unit level for production plant and at the account or sub-account level for all other plant and is based on the average life group method. In 2020, the provision for depreciation is projected to be 2.7 percent of the average depreciable utility plant. Amortization of intangible assets is calculated using the straight-line method. Of the remaining amortizable intangible plant balance at December 31, 2019, 98.9 percent will be amortized over 10.4 years with the remaining 1.1 percent of the intangible plant balance at December 31, 2019 being amortized over 23.7 years. Amortization of plant acquisition adjustments is provided on a straight-line basis over the estimated remaining service life of the acquired assets. Plant acquisition adjustments include $148.3 million for the Redbud Plant, which is being amortized over a 27 year life and $3.3 million for certain transmission substation facilities in OG&E's service territory, which are being amortized over a 37 to 59 year period. Allowance for Funds Used During Construction Allowance for funds used during construction, a non-cash item, is reflected as an increase to Net Other Income and a reduction to Interest Expense in the Statements of Income and as an increase to Construction Work in Progress in the Balance Sheets. Allowance for funds used during construction is calculated according to the FERC requirements for the imputed cost of equity and borrowed funds. Allowance for funds used during construction rates, compounded semi-annually, were 7.6 percent, 7.6 percent and 8.2 percent for the years ended December 31, 2019, 2018 and 2017, respectively. Collection of Sales Tax In the normal course of its operations, OG&E collects sales tax from its customers. OG&E records a current liability for sales taxes when it bills its customers and eliminates this liability when the taxes are remitted to the appropriate governmental authorities. OG&E excludes the sales tax collected from its operating revenues. Revenue Recognition General OG&E recognizes revenue from electric sales when power is delivered to customers. The performance obligation to deliver electricity is generally created and satisfied simultaneously, and the provisions of the regulatory-approved tariff determine the charges OG&E may bill the customer, payment due date and other pertinent rights and obligations of both parties. OG&E reads its customers' meters and sends bills to its customers throughout each month. As a result, there is a significant amount of customers' electricity consumption that has not been billed at the end of each month. OG&E accrues an estimate of the revenues for electric sales delivered since the latest billings. Unbilled revenue is presented in Accrued Unbilled Revenues in the Balance Sheets and in Revenues from Contracts with Customers in the Statements of Income based on estimates of usage and prices during the period. The estimates that management uses in this calculation could vary from the actual amounts to be paid by customers. Integrated Market and Transmission OG&E currently owns and operates transmission and generation facilities as part of a vertically integrated utility. OG&E is a member of the SPP regional transmission organization and has transferred operational authority, but not ownership, of OG&E's transmission facilities to the SPP. The SPP has implemented FERC-approved regional day-ahead and real-time markets for energy and operating services, as well as associated transmission congestion rights. Collectively the three markets operate together under the global name, SPP Integrated Marketplace. OG&E represents owned and contracted generation assets and customer load in the SPP Integrated Marketplace for the sole benefit of its customers. OG&E has not participated in the SPP Integrated Marketplace for any speculative trading activities. OG&E records the SPP Integrated Marketplace transactions as sales or purchases per FERC Order 668, which requires that purchases and sales be recorded on a net basis for each settlement period of the SPP Integrated Marketplace. Purchases and sales are based on the fixed transaction price determined by the market at the time of the purchase or sale and the MWh quantity purchased or sold. These results are reported as Revenues from Contracts with Customers or Cost of Sales in the Financial Statements. OG&E revenues, expenses, assets and liabilities may be adversely affected by changes in the organization, operating and regulation by the FERC or the SPP. OG&E's transmission revenues are generated by the use of OG&E's transmission network by the SPP, which operates the network, on behalf of other transmission owners. OG&E recognizes revenue on the sale of transmission service to its customers over time as the service is provided in the amount OG&E has a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by OG&E's FERC-approved formula transmission rates along with other SPP-specific charges and the megawatt quantity reserved. Other Revenues Revenues from Alternative Revenue Programs Other Revenues in the Statements of Income is comprised of certain rider revenue that includes alternative revenue measures as defined in ASC 980, "Regulated Operations," which details two types of alternative revenue programs. The first type adjusts billings for the effects of weather abnormalities or broad external factors or to compensate OG&E for demand-side management initiatives (i.e., no-growth plans and similar conservation efforts). The second type provides for additional billings (i.e., incentive awards) for the achievement of certain objectives, such as reducing costs, reaching specified milestones or demonstratively improving customer service. Once the specific events permitting billing of the additional revenues under either program type have been completed, OG&E recognizes the additional revenues if (i) the program is established by an order from OG&E's regulatory commission that allows for automatic adjustment of future rates; (ii) the amount of additional revenues for the period is objectively determinable and is probable of recovery; and (iii) the additional revenues will be collected within 24 months following the end of the annual period in which they are recognized. Fuel Adjustment Clauses The actual cost of fuel used in electric generation and certain purchased power costs are passed through to OG&E's customers through fuel adjustment clauses. The fuel adjustment clauses are subject to periodic review by the OCC and the APSC. Leases OG&E evaluates all contracts under ASC 842 to determine if the contract is or contains a lease and to determine classification as an operating or finance lease. If a lease is identified, OG&E recognizes a right-of-use asset and a lease liability in its Balance Sheets. OG&E recognizes and measures a lease liability when it concludes the contract contains an identified asset that OG&E controls through having the right to obtain substantially all of the economic benefits and the right to direct the use of the identified asset. The liability is equal to the present value of lease payments, and the asset is based on the liability, subject to adjustment, such as for initial direct costs. Further, OG&E utilizes an incremental borrowing rate for purposes of measuring lease liabilities, if the discount rate is not implicit in the lease. To calculate the incremental borrowing rate, OG&E starts with a current pricing report for OG&E's senior unsecured notes, which indicates rates for periods reflective of the lease term, and adjusts for the effects of collateral to arrive at the secured incremental borrowing rate. As permitted by ASC 842, OG&E made an accounting policy election to not apply the balance sheet recognition requirements to short-term leases and to not separate lease components from nonlease components when recognizing and measuring lease liabilities. For income statement purposes, OG&E records operating lease expense on a straight-line basis. Accrued Vacation OG&E accrues vacation pay monthly by establishing a liability for vacation earned. Vacation may be taken as earned and is charged against the liability. At the end of each year, the liability represents the amount of vacation earned but not taken.
Use of Estimates, Policy [Policy Text Block]	Use of EstimatesIn preparing the Financial Statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Changes to these assumptions and estimates could have a material effect on OG&E's Financial Statements. However, OG&E believes it has taken reasonable positions where assumptions and estimates are used in order to minimize the negative financial impact to OG&E that could result if actual results vary from the assumptions and estimates. In management's opinion, the areas of OG&E where the most significant judgment is exercised include the determination of Pension Plan assumptions, income taxes, contingency reserves, asset retirement obligations, depreciable lives of property, plant and equipment, regulatory assets and liabilities and unbilled revenues.

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 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. December 31 (In millions) 2019 2018 REGULATORY ASSETS Current: Fuel clause under recoveries $ 39.5 $ 2.0 Production tax credit rider over credit (A) 1.7 6.9 Oklahoma demand program rider under recovery (A) — 6.4 Other (A) 7.5 3.2 Total current regulatory assets $ 48.7 $ 18.5 Non-current: Benefit obligations regulatory asset $ 167.2 $ 188.2 Deferred storm expenses 65.5 36.5 Sooner Dry Scrubbers 20.6 4.5 Smart Grid 18.4 25.6 Unamortized loss on reacquired debt 10.6 11.4 Arkansas deferred pension expenses 8.0 6.8 Pension tracker 2.3 — Other 13.4 12.8 Total non-current regulatory assets $ 306.0 $ 285.8 REGULATORY LIABILITIES Current: Reserve for tax refund and interim surcharge (B) $ 12.7 $ 15.4 Fuel clause over recoveries 4.8 0.3 SPP cost tracker over recovery (B) 2.6 16.8 Oklahoma demand program rider over recovery (B) 2.0 — Transmission cost recovery rider over recovery (B) — 2.7 Other (B) 6.9 1.4 Total current regulatory liabilities $ 29.0 $ 36.6 Non-current: Income taxes refundable to customers, net $ 899.2 $ 937.1 Accrued removal obligations, net 318.5 308.1 Pension tracker — 18.7 Other 5.8 6.8 Total non-current regulatory liabilities $ 1,223.5 $ 1,270.7 (A) Included in Other Current Assets in the Balance Sheets.
Components of Benefit Obligation Regulatory Asset [Table Text Block]	The following table is a summary of the components of the benefit obligations regulatory asset: December 31 (In millions) 2019 2018 Pension Plan and Restoration of Retirement Income Plan: Net loss $ 160.5 $ 185.3 Postretirement Benefit Plans: Net loss 23.3 25.6 Prior service cost (16.6) (22.7) Total $ 167.2 $ 188.2
Schedule of Net Periodic Benefit Cost Not yet Recognized [Table Text Block]	The following amounts in the benefit obligations regulatory asset at December 31, 2019 are expected to be recognized as components of net periodic benefit cost in 2020: (In millions) Pension Plan and Restoration of Retirement Income Plan: Net loss $ 11.4 Postretirement Benefit Plans: Net loss 2.8 Prior service cost (6.1) Total $ 8.1
Schedule of Jointly Owned Utility Plants [Table Text Block]	The tables below 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, 2019 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 254.4 $ 83.5 $ 170.9 Redbud Plant (A)(B) 51 % $ 529.9 $ 159.0 $ 370.9 (A) Construction work in progress was $0.2 million and $1.4 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. December 31, 2018 (In millions) Percentage Ownership Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment McClain Plant (A) 77 % $ 227.2 $ 78.2 $ 149.0 Redbud Plant (A)(B) 51 % $ 493.9 $ 145.3 $ 348.6 (A) Construction work in progress was $0.2 million and $0.9 million for the McClain and Redbud Plants, respectively. (B) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $56.3 million.
Property, Plant and Equipment [Table Text Block]	OG&E's property, plant and equipment and related accumulated depreciation are divided into the following major classes: December 31, 2019 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment Distribution assets $ 4,468.6 $ 1,381.1 $ 3,087.5 Electric generation assets (A) 4,838.6 1,601.0 3,237.6 Transmission assets (B) 2,901.1 565.5 2,335.6 Intangible plant 225.2 145.4 79.8 Other property and equipment 473.1 175.1 298.0 Total property, plant and equipment $ 12,906.6 $ 3,868.1 $ 9,038.5 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.8 million. December 31, 2018 (In millions) Total Property, Plant and Equipment Accumulated Depreciation Net Property, Plant and Equipment Distribution assets $ 4,229.4 $ 1,324.5 $ 2,904.9 Electric generation assets (A) 4,657.2 1,572.8 3,084.4 Transmission assets (B) 2,846.7 534.2 2,312.5 Intangible plant 187.6 135.1 52.5 Other property and equipment 444.2 160.8 283.4 Total property, plant and equipment $ 12,365.1 $ 3,727.4 $ 8,637.7 (A) This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $56.3 million. (B) This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.7 million.
Schedule of Change in Asset Retirement Obligation [Table Text Block]	The following table summarizes changes to OG&E's asset retirement obligations during the years ended December 31, 2019 and 2018. (In millions) 2019 2018 Balance at January 1 $ 83.9 $ 75.1 Accretion expense 1.0 3.4 Revisions in estimated cash flows (A) (2.4) 6.8 Liabilities settled (B) (9.0) (1.4) Balance at December 31 $ 73.5 $ 83.9 (A) Assumptions changed related to the estimated cost of the removal of wind turbine assets and asbestos removal at OG&E's generating facilities.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	The following table disaggregates OG&E's revenues from contracts with customers by customer classification. OG&E's operating revenues disaggregated by customer classification can be found in "OG&E (Electric Utility) Results of Operations" within "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations." Year Ended December 31, (In millions) 2019 2018 Residential $ 865.8 $ 877.8 Commercial 486.6 500.0 Industrial 217.8 228.9 Oilfield 200.4 190.4 Public authorities and street light 190.3 197.4 System sales revenues 1,960.9 1,994.5 Provision for rate refund (0.9) (6.0) Integrated market 38.4 48.7 Transmission 148.0 147.4 Other 29.1 27.1 Revenues from contracts with customers $ 2,175.5 $ 2,211.7

Related-Party Transactions Re_2

Related-Party Transactions Related-Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2019
Related Party Transaction [Line Items]
Schedule of Related Party Transactions [Table Text Block]	The following table summarizes related party transactions between OG&E and Enable during the years ended December 31, 2019, 2018 and 2017. Year Ended December 31, (In millions) 2019 2018 2017 Operating revenues: Electricity to power electric compression assets $ 15.9 $ 16.3 $ 14.0 Cost of sales: Natural gas transportation services $ 41.2 $ 37.9 $ 35.0 Natural gas (sales) purchases $ (6.0) $ (3.2) $ (2.1)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping [Table Text Block]	The following table summarizes the carrying amount and fair value of OG&E's financial instruments at December 31, 2019 and 2018, as well as the classification level within the fair value hierarchy. 2019 2018 December 31 (In millions) Carrying Fair Carrying Fair Classification Long-term Debt (including Long-term Debt due within one year): Senior Notes $ 3,050.3 $ 3,500.4 $ 3,001.9 $ 3,178.2 Level 2 Industrial Authority Bonds $ 135.4 $ 135.4 $ 135.4 $ 135.4 Level 2 Tinker Debt $ 9.5 $ 10.0 $ 9.6 $ 8.7 Level 3

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	The following table summarizes OG&E's pre-tax compensation expense and related income tax benefit for the years ended December 31, 2019, 2018 and 2017 related to performance units and restricted stock units for OG&E employees. Year Ended December 31 (In millions) 2019 2018 2017 Performance units: Total shareholder return $ 3.0 $ 2.8 $ 2.5 Earnings per share 1.5 1.8 0.5 Total performance units 4.5 4.6 3.0 Restricted stock units 0.4 — — Total compensation expense $ 4.9 $ 4.6 $ 3.0 Income tax benefit $ 1.3 $ 1.2 $ 1.2
Performance Units Total Shareholder Return Valuation Assumptions [Table Text Block]	The number of performance units granted based on total shareholder return and the assumptions used to calculate the grant date fair value of the performance units based on total shareholder return are shown in the following table. 2019 2018 2017 Number of units granted to OG&E employees 68,396 91,940 85,501 Fair value of units granted $ 47.00 $ 36.86 $ 41.76 Expected dividend yield 4.0 % 3.6 % 3.8 % Expected price volatility 17.0 % 19.0 % 19.8 % Risk-free interest rate 2.47 % 2.38 % 1.46 % Expected life of units (in years) 2.86 2.86 2.86
Performance Units Earnings Per Share Valuation Assumptions [Table Text Block]	In 2019, the Compensation Committee of OGE Energy's Board of Directors voted to grant restricted stock units in lieu of performance units based on earnings per share. For 2018 and 2017, the number of performance units granted based on earnings per share and the grant date fair value are shown in the following table. 2018 2017 Number of units granted to OG&E employees 30,649 28,499 Fair value of units granted $ 31.03 $ 34.83
Share-based Compensation, Activity [Table Text Block]	A summary of the activity for OGE Energy's performance units and restricted stock units applicable to OG&E's employees at December 31, 2019 and changes in 2019 are shown in the following table. Performance Units Restricted Total Shareholder Return Earnings Per Share (Dollars in millions) Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Number Aggregate Intrinsic Value Units/shares outstanding at 12/31/18 261,423 87,143 312 Granted 68,396 (A) — 26,141 Converted (95,593) (B) $ 7.0 (31,865) (B) $ 2.5 N/A Vested N/A N/A (312) $ — Forfeited (10,360) (2,207) (1,500) Employee migration 3,813 (C) 906 (C) 364 (C) Units/shares outstanding at 12/31/19 227,679 $ 12.2 53,977 $ 4.0 25,005 $ 1.1 Units/shares fully vested at 12/31/19 77,799 $ 4.0 25,931 $ 2.3 (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) These amounts represent performance units that vested at December 31, 2018 which were settled in February 2019.
Schedule of Nonvested Share Activity [Table Text Block]	A summary of the activity for OGE Energy's non-vested performance units and restricted stock units applicable to OG&E's employees at December 31, 2019 and changes in 2019 are shown in the following table. Performance Units Restricted Total Shareholder Return Earnings Per Share Number Weighted-Average Number Weighted-Average Number Weighted-Average Units/shares non-vested at 12/31/18 165,830 $ 39.17 55,278 $ 32.82 312 $ 31.88 Granted 68,396 (A) $ 47.00 — $ — 26,141 $ 41.63 Vested (77,799) $ 41.76 (25,931) $ 34.83 (312) $ 31.88 Forfeited (10,360) $ 41.33 (2,207) $ 32.02 (1,500) $ 41.78 Employee migration 3,813 (B) $ 41.43 906 (B) $ 32.84 364 (B) $ 41.78 Units/shares non-vested at 12/31/19 149,880 $ 41.31 28,046 $ 31.03 25,005 $ 41.62 Units/shares expected to vest 145,790 (C) 28,006 (C) 20,251 (C) (A) For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target. (B) Due to certain employees transferring between OG&E and OGE Energy. (C) The intrinsic value of the performance units based on total shareholder return and earnings per share is $8.1 million and $1.7 million, respectively. The intrinsic value of restricted stock units is $0.9 million.
Fair Value of Vested Performance Units and Restricted Stock [Table Text Block]	A summary of OG&E's fair value for its vested performance units and restricted stock units is shown in the following table. Year Ended December 31 (In millions) 2019 2018 2017 Performance units: Total shareholder return $ 3.2 $ 2.1 $ 2.3 Earnings per share $ 0.9 $ 1.7 $ 0.4 Restricted stock units $ — $ — $ 0.1
Schedule of Unrecognized Compensation Cost, Nonvested Awards [Table Text Block]	A summary of OG&E's unrecognized compensation cost for its non-vested performance units and restricted stock units and the weighted-average periods over which the compensation cost is expected to be recognized are shown in the following table. December 31, 2019 Unrecognized Compensation Cost (In millions) Weighted Average to be Recognized (In years) Performance units: Total shareholder return $ 3.0 1.68 Earnings per share 0.3 1.00 Total performance units 3.3 Restricted stock units 0.7 2.00 Total unrecognized compensation cost $ 4.0

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]		The items comprising income tax expense (benefit) are as follows: Year Ended December 31 (In millions) 2019 2018 2017 Provision (benefit) for current income taxes: Federal $ (7.9) $ (12.4) $ 26.3 State 4.1 (4.1) (4.3) Total provision (benefit) for current income taxes (3.8) (16.5) 22.0 Provision (benefit) for deferred income taxes, net: Federal 37.7 53.7 100.0 State (13.8) 2.7 19.9 Total provision for deferred income taxes, net 23.9 56.4 119.9 Deferred federal investment tax credits, net — 0.1 (0.1) Total income tax expense $ 20.1 $ 40.0 $ 141.8
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]		The following schedule reconciles the statutory tax rates to the effective income tax rate: Year Ended December 31 2019 2018 2017 Statutory federal tax rate 21.0 % 21.0 % 35.0 % Federal renewable energy credit (A) (7.6) (6.9) (6.1) Amortization of net unfunded deferred taxes (5.6) (2.9) 0.9 State income taxes, net of federal income tax benefit (1.8) (0.2) 2.2 Other (0.6) (0.1) (0.3) Effective income tax rate 5.4 % 10.9 % 31.7 % (A) Represents credits associated with the production from OG&E's wind farms.
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]		The components of Deferred Income Taxes at December 31, 2019 and 2018 were as follows: December 31 (In millions) 2019 2018 Deferred income tax liabilities, net: Accelerated depreciation and other property related differences $ 1,656.8 $ 1,605.3 Regulatory assets 28.4 17.4 OG&E Pension Plan 24.5 26.0 Bond redemption-unamortized costs 2.2 2.4 Federal tax credits (238.0) (237.5) Income taxes recoverable from customers, net (229.9) (239.6) State tax credits (170.8) (142.3) Regulatory liabilities (68.1) (78.8) Asset retirement obligations (19.2) (21.5) Postretirement medical and life insurance benefits (16.0) (16.2) Net operating losses (5.7) (10.0) Other (4.7) (2.4) Accrued liabilities (4.3) (6.1) Deferred federal investment tax credits (1.8) (1.9) Accrued vacation (1.6) (1.7) Uncollectible accounts (0.4) (0.4) Total deferred income tax liabilities, net $ 951.4 $ 892.7
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	Following is a reconciliation of OG&E’s total gross unrecognized tax benefits as of the years ended December 31, 2019, 2018 and 2017. (In millions) 2019 2018 2017 Balance at January 1 $ 20.7 $ 20.7 $ 20.7 Tax positions related to current year: Additions — — — Balance at December 31 $ 20.7 $ 20.7 $ 20.7
Summary of Tax Credit Carryforwards [Table Text Block]		The following table summarizes these carry forwards: (In millions) Carry Forward Amount Deferred Tax Asset Earliest Expiration Date State operating loss $ 127.3 $ 5.7 2030 Federal tax credits $ 238.0 $ 238.0 2032 State tax credits: Oklahoma investment tax credits $ 165.1 $ 130.4 N/A Oklahoma capital investment board credits $ 12.4 $ 12.4 N/A Oklahoma zero emission tax credits $ 34.9 $ 28.0 2020 N/A - not applicable

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Long-term Debt, Unclassified [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	OG&E has tax-exempt pollution control bonds with optional redemption provisions that allow the holders to request repayment of the bonds on any business day. The bonds, which can be tendered at the option of the holder during the next 12 months, are as follows: Series Date Due Amount (In millions) 1.20% - 2.50% Garfield Industrial Authority, January 1, 2025 $ 47.0 1.19% - 2.35% Muskogee Industrial Authority, January 1, 2025 32.4 1.20% - 2.48% Muskogee Industrial Authority, June 1, 2027 56.0 Total (redeemable during next 12 months) $ 135.4

Retirement Plans and Postreti_2

Retirement Plans and Postretirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	The following table presents the status of OGE Energy's Pension Plan, the Restoration of Retirement Income Plan and the postretirement benefit plans for 2019 and 2018. These amounts have been recorded in Accrued Benefit Obligations with the offset recorded as a regulatory asset in OG&E's Balance Sheets as discussed in Note 1. The regulatory asset represents a net periodic benefit cost to be recognized in the Statements of Income in future periods. OG&E's portion of the benefit obligation for OGE Energy's Pension Plan and the Restoration of Retirement Income Plan represents the projected benefit obligation, while the benefit obligation for the postretirement benefit plans represents the accumulated postretirement benefit obligation. The accumulated postretirement benefit obligation for OG&E's Pension Plan and Restoration of Retirement Income Plan differs from the projected benefit obligation in that the former includes no assumption about future compensation levels. The accumulated postretirement benefit obligation for the Pension Plan and the Restoration of Retirement Income Plan at December 31, 2019 was $425.8 million and $4.8 million, respectively. The accumulated postretirement benefit obligation for the Pension Plan and the Restoration of Retirement Income Plan at December 31, 2018 was $417.6 million and $5.0 million, respectively. The details of the funded status of the Pension Plan, the Restoration of Retirement Income Plan and the postretirement benefit plans and the amounts included in the Balance Sheets are included in the following table. Pension Plan Restoration of Retirement Postretirement December 31 (In millions) 2019 2018 2019 2018 2019 2018 Change in benefit obligation Beginning obligations $ 453.6 $ 510.6 $ 6.0 $ 4.2 $ 104.8 $ 115.8 Service cost 9.0 9.8 0.2 0.2 0.2 0.2 Interest cost 15.6 17.6 0.2 0.2 4.3 4.2 Plan settlements (45.6) (52.6) (0.9) (0.6) — — Participants' contributions — — — — 3.0 2.9 Actuarial losses (gains) 42.1 (19.0) 0.6 2.0 2.2 (6.5) Benefits paid (12.7) (12.8) — — (9.8) (11.8) Ending obligations $ 462.0 $ 453.6 $ 6.1 $ 6.0 $ 104.7 $ 104.8 Change in plans' assets Beginning fair value $ 387.6 $ 477.2 $ — $ — $ 40.6 $ 45.2 Actual return on plans' assets 64.8 (29.2) — — 4.0 (0.5) Employer contributions 5.0 5.0 0.9 0.6 4.1 4.8 Plan settlements (45.6) (52.6) (0.9) (0.6) — — Participants' contributions — — — — 3.0 2.9 Benefits paid (12.7) (12.8) — — (9.8) (11.8) Ending fair value $ 399.1 $ 387.6 $ — $ — $ 41.9 $ 40.6 Funded status at end of year $ (62.9) $ (66.0) $ (6.1) $ (6.0) $ (62.8) $ (64.2)
Schedule of Defined Benefit Plans Disclosures [Table Text Block]	The following table presents the net periodic benefit cost components, before consideration of capitalized amounts, of OG&E's Pension Plan, Restoration of Retirement Income Plan and postretirement benefit plans that are included in the Financial Statements. Service cost is presented within Other Operation and Maintenance, and interest cost, expected return on plan assets, amortization of net loss, amortization of unrecognized prior service cost and settlement cost are presented within Other Net Periodic Benefit Expense in OG&E's Statements of Income. OG&E recovers specific amounts of pension and postretirement medical costs in rates approved in its Oklahoma rate reviews. In accordance with approved orders, OG&E defers the difference between actual pension and postretirement medical expenses and the amount approved in its last Oklahoma rate review as a regulatory asset or regulatory liability. These amounts have been recorded in the Pension tracker in the regulatory assets and liabilities table in Note 1 and within Other Net Periodic Benefit Expense in OG&E's Statements of Income. Pension Plan Restoration of Retirement Postretirement Benefit Plans Year Ended December 31 (In millions) 2019 2018 2017 2019 2018 2017 2019 2018 2017 Service cost $ 9.0 $ 9.8 $ 10.1 $ 0.2 $ 0.2 $ 0.1 $ 0.2 $ 0.2 $ 0.4 Interest cost 15.6 17.6 19.5 0.2 0.2 0.2 4.3 4.2 5.6 Expected return on plan assets (27.6) (33.1) (32.8) — — — (1.7) (1.8) (2.0) Amortization of net loss 12.9 12.1 13.0 0.3 0.5 0.4 2.1 3.8 1.9 Amortization of unrecognized prior service cost (A) — — — — — — (6.1) (6.1) (2.5) Settlement cost 16.4 19.4 11.7 0.5 0.4 — — — 0.4 Total net periodic benefit cost 26.3 25.8 21.5 1.2 1.3 0.7 (1.2) 0.3 3.8 Plus: Amount allocated from OGE Energy 4.5 5.7 — 0.5 1.2 — (0.6) (0.7) — Net periodic benefit cost $ 30.8 $ 31.5 $ 21.5 $ 1.7 $ 2.5 $ 0.7 $ (1.8) $ (0.4) $ 3.8 (A) Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment. In addition to the net periodic benefit cost amounts recognized, as presented in the table above, for the Pension and Restoration of Retirement Income Plans in 2019, 2018 and 2017, OG&E recognized the following: Year Ended December 31 (In millions) 2019 2018 2017 Decrease of pension expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ (16.1) $ (14.1) $ (2.3) Deferral of pension expense related to pension settlement charges: Oklahoma jurisdiction (A) $ 17.9 $ 22.1 $ 13.2 Arkansas jurisdiction (A) $ 1.7 $ 2.1 $ 1.1 (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1. In addition to the net periodic benefit income and cost amounts recognized, as presented in the table above, for the postretirement benefit plans in 2019, 2018 and 2017, OG&E recognized the following: Year Ended December 31 ( In millions ) 2019 2018 2017 Increase of postretirement expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) $ 1.0 $ 4.4 $ 6.2 (A) Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.
Schedule of Capitalized Pension and Postretirement Cost [Table Text Block]	(In millions) 2019 2018 2017 Capitalized portion of net periodic pension benefit cost $ 3.0 $ 3.2 $ 3.4 Capitalized portion of net periodic postretirement benefit cost $ 0.1 $ 0.1 $ 1.1
Schedule of Assumptions Used [Table Text Block]	Rate Assumptions Pension Plan and Postretirement Year Ended December 31 2019 2018 2017 2019 2018 2017 Assumptions to determine benefit obligations: Discount rate 3.15 % 4.20 % 3.60 % 3.25 % 4.30 % 3.70 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A N/A Assumptions to determine net periodic benefit cost: Discount rate 3.63 % 3.73 % 4.00 % 4.30 % 3.70 % 4.20 % Expected return on plan assets 7.50 % 7.50 % 7.50 % 4.00 % 4.00 % 4.00 % Rate of compensation increase 4.20 % 4.20 % 4.20 % N/A N/A 4.20 % N/A - not applicable
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]	The effects of a one-percentage point change in the assumed health care cost trend rate are presented in the following tables. ONE-PERCENTAGE POINT INCREASE Year Ended December 31 (In millions) 2019 2018 2017 Effect on aggregate of the service and interest cost components $ — $ — $ — Effect on accumulated postretirement benefit obligations $ 0.1 $ 0.1 $ 0.1 ONE-PERCENTAGE POINT DECREASE Year Ended December 31 (In millions) 2019 2018 2017 Effect on aggregate of the service and interest cost components $ — $ — $ — Effect on accumulated postretirement benefit obligations $ 0.2 $ 0.2 $ 0.2
Projected Benefit Obligation Funded Status Thresholds [Table Text Block]	The Pension Plan assets are held in a trust which follows an investment policy and strategy designed to reduce the funded status volatility of the Plan by utilizing liability driven investing. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The investment policy follows a glide path approach that shifts a higher portfolio weighting to fixed income as the Plan's funded status increases. The table below sets forth the targeted fixed income and equity allocations at different funded status levels. Projected Benefit Obligation Funded Status Thresholds <90% 95% 100% 105% 110% 115% 120% Fixed income 50% 58% 65% 73% 80% 85% 90% Equity 50% 42% 35% 27% 20% 15% 10% Total 100% 100% 100% 100% 100% 100% 100%
Pension Plan Equity Asset Allocation Table [Table Text Block]	Within the portfolio's overall allocation to equities, the funds are allocated according to the guidelines in the table below. Asset Class Target Allocation Minimum Maximum Domestic Large Cap Equity 40% 35% 60% Domestic Mid-Cap Equity 15% 5% 25% Domestic Small-Cap Equity 25% 5% 30% International Equity 20% 10% 30%
Schedule of Allocation of Plan Assets [Table Text Block]	The following tables summarize OG&E's portion of OGE Energy's Pension Plan's investments that are measured at fair value on a recurring basis at December 31, 2019 and 2018. There were no Level 3 investments held by the Pension Plan at December 31, 2019 and 2018. (In millions) December 31, 2019 Level 1 Level 2 Net Asset Value (A) Common stocks $ 202.0 $ 202.0 $ — $ — U.S. Treasury notes and bonds (B) 134.8 134.8 — — Mortgage- and asset-backed securities 45.8 — 45.8 — Corporate fixed income and other securities 130.5 — 130.5 — Commingled fund (C) 23.9 — — 23.9 Foreign government bonds 3.0 — 3.0 — U.S. municipal bonds 1.1 — 1.1 — Money market fund 7.5 — — 7.5 Mutual fund 2.4 2.4 — — Preferred stocks 0.7 0.7 — — Futures: U.S. Treasury futures (receivable) 22.9 — 22.9 — U.S. Treasury futures (payable) (10.9) — (10.9) — Cash collateral 0.6 0.6 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 564.4 $ 340.5 $ 192.5 $ 31.4 Interest and dividends receivable 2.4 Payable to broker for securities purchased (36.5) Pension Plan investments attributable to affiliates (131.2) Total Pension Plan assets $ 399.1 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. (In millions) December 31, 2018 Level 1 Level 2 Net Asset Value (A) Common stocks $ 169.3 $ 169.3 $ — $ — U.S. Treasury notes and bonds (B) 137.9 137.9 — — Mortgage- and asset-backed securities 65.9 — 65.9 — Corporate fixed income and other securities 143.2 — 143.2 — Commingled fund (C) 19.7 — — 19.7 Foreign government bonds 4.4 — 4.4 — U.S. municipal bonds 0.6 — 0.6 — Money market fund 0.3 — — 0.3 Mutual fund 8.0 8.0 — — Futures: U.S. Treasury futures (receivable) 27.0 — 27.0 — U.S. Treasury futures (payable) (20.4) — (20.4) — Cash collateral 0.7 0.7 — — Forward contracts: Receivable (foreign currency) 0.1 — 0.1 — Total Pension Plan investments 556.7 $ 315.9 $ 220.8 $ 20.0 Interest and dividends receivable 3.0 Payable to broker for securities purchased (36.9) Pension Plan investments attributable to affiliates (135.2) Total Pension Plan assets $ 387.6 (A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy. (B) This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher. (C) This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets. The following tables summarize OG&E's portion of OGE Energy's postretirement benefit plans' investments that are measured at fair value on a recurring basis at December 31, 2019 and 2018. There were no Level 2 investments held by the postretirement benefit plans at December 31, 2019 and 2018. (In millions) December 31, 2019 Level 1 Level 3 Group retiree medical insurance contract $ 34.8 $ — $ 34.8 Mutual funds 10.9 10.9 — Money market fund 1.2 1.2 — Total plan investments 46.9 $ 12.1 $ 34.8 Plan investments attributable to affiliates (5.0) Total plan assets $ 41.9 (In millions) December 31, 2018 Level 1 Level 3 Group retiree medical insurance contract $ 36.0 $ — $ 36.0 Mutual funds 8.9 8.9 — Cash 0.9 0.9 — Total plan investments 45.8 $ 9.8 $ 36.0 Plan investments attributable to affiliates (5.2) Total plan assets $ 40.6
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block]	The following table summarizes the postretirement benefit plans' investments that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Year Ended December 31 (In millions) 2019 Group retiree medical insurance contract: Beginning balance $ 36.0 Claims paid (3.8) Investment fees (0.1) Net unrealized gains related to instruments held at the reporting date 1.4 Interest income 0.8 Dividend income 0.5 Ending balance $ 34.8
Schedule of Expected Benefit Payments [Table Text Block]	The following table summarizes the benefit payments OG&E expects to pay related to OGE Energy's Pension Plan and Restoration of Retirement Income Plan. These expected benefits are based on the same assumptions used to measure OGE Energy's benefit obligation at the end of the year and include benefits attributable to estimated future employee service. (In millions) Projected Benefit Payments 2020 $ 44.6 2021 $ 44.2 2022 $ 42.5 2023 $ 42.2 2024 $ 42.0 After 2024 $ 179.8 The Medicare Prescription Drug, Improvement and Modernization Act of 2003 expanded coverage for prescription drugs. The following table summarizes the gross benefit payments OG&E expects to pay related to its postretirement benefit plans, including prescription drug benefits. (In millions) Gross Projected 2020 $ 8.9 2021 $ 8.9 2022 $ 8.8 2023 $ 7.4 2024 $ 7.3 After 2024 $ 32.4

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Unrecorded Unconditional Purchase Obligations Disclosure [Table Text Block]		Purchase Obligations and Commitments OG&E's future purchase obligations and commitments estimated for the next five years are as follows: (In millions) 2020 2021 2022 2023 2024 Total Purchase obligations and commitments: Minimum purchase commitments $ 82.6 $ 55.1 $ 50.4 $ 50.4 $ 32.9 $ 271.4 Expected wind purchase commitments 55.7 56.0 56.4 56.8 57.5 282.4 Long-term service agreement commitments 2.4 2.4 2.4 13.8 32.1 53.1 Environmental compliance plan expenditures 0.4 — — — — 0.4 Total purchase obligations and commitments $ 141.1 $ 113.5 $ 109.2 $ 121.0 $ 122.5 $ 607.3
Schedule of Wind Power Purchases [Table Text Block]	The following table summarizes OG&E's wind power purchase contracts. Company Location Original Term of Contract Expiration of Contract MWs CPV Keenan Woodward County, OK 20 years 2030 152.0 Edison Mission Energy Dewey County, OK 20 years 2031 130.0 NextEra Energy Blackwell, OK 20 years 2032 60.0 The following table summarizes OG&E's wind power purchases for the years ended December 31, 2019, 2018 and 2017. Year Ended December 31 (In millions) 2019 2018 2017 CPV Keenan $ 27.2 $ 27.0 $ 29.0 Edison Mission Energy 23.1 21.7 22.1 NextEra Energy 7.4 6.8 7.4 FPL Energy (A) — 2.1 2.6 Total wind power purchased $ 57.7 $ 57.6 $ 61.1

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	Due to the seasonal fluctuations and other factors of OG&E's business, the operating results for interim periods are not necessarily indicative of the results that may be expected for the year. In OG&E's opinion, the following quarterly financial data includes all adjustments, consisting of normal recurring adjustments, necessary to fairly present such amounts. Summarized quarterly unaudited financial data is as follows: Quarter Ended ( In millions) March 31 June 30 September 30 December 31 Total Operating revenues 2019 $ 490.0 $ 513.7 $ 755.4 $ 472.5 $ 2,231.6 2018 $ 492.7 $ 567.0 $ 698.8 $ 511.8 $ 2,270.3 Operating income 2019 $ 50.3 $ 110.6 $ 275.0 $ 71.8 $ 507.7 2018 $ 67.1 $ 138.3 $ 230.3 $ 58.5 $ 494.2 Net income 2019 $ 19.6 $ 74.5 $ 227.2 $ 28.9 $ 350.2 2018 $ 31.3 $ 92.0 $ 183.9 $ 20.8 $ 328.0

Schedule II (Tables)

Schedule II (Tables)	9 Months Ended
	Sep. 30, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule II Valuation and Qualifying Accounts [Table Text Block]	SCHEDULE II - Valuation and Qualifying Accounts Additions Description Balance at Beginning of Period Charged to Costs and Expenses Deductions (A) Balance at End of Period (In millions) Balance at December 31, 2017 Reserve for Uncollectible Accounts $ 1.5 $ 2.6 $ 2.6 $ 1.5 Balance at December 31, 2018 Reserve for Uncollectible Accounts $ 1.5 $ 3.4 $ 3.2 $ 1.7 Balance at December 31, 2019 Reserve for Uncollectible Accounts $ 1.7 $ 2.2 $ 2.4 $ 1.5

Leases, Codification Topic 842

Leases, Codification Topic 842 (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lease, Cost	The following table presents amounts recognized for operating leases in OG&E's 2019 Cash Flow Statement and Balance Sheet and supplemental information related to those amounts recognized, as well as a maturity analysis of OG&E's operating lease liabilities. (In millions) Year Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 4.8 Right-of-use assets obtained in exchange for new operating lease liabilities $ 10.7 (Dollars in millions) December 31, 2019 Right-of-use assets at period end (A) $ 39.6 Operating lease liabilities at period end (B) $ 44.3 Operating lease weighted-average remaining lease term (in years) 13.5 Operating lease weighted-average discount rate 3.9 % December 31, Future minimum operating lease payments as of: 2019 2018(C)(D) (In millions) 2019 $ — $ 21.1 2020 5.3 2.9 2021 5.2 2.9 2022 5.2 2.9 2023 5.2 2.9 2024 3.1 3.0 Thereafter 34.7 34.6 Total future minimum lease payments 58.7 $ 70.3 Less: Imputed interest 14.4 Present value of net minimum lease payments $ 44.3 (A) Included in Property, Plant and Equipment in the 2019 Balance Sheet. (B) Included in Other Deferred Credits and Other Liabilities in the 2019 Balance Sheet. (C) Amounts included for comparability and accounted for in accordance with ASC 840, "Leases."

Summary of Significant Accoun_6

Summary of Significant Accounting Policies Regulated Operations (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Schedule of Regulatory Assets and Liabilities [Line Items]
Fuel clause under recoveries		$ 39.5	$ 2
Fuel clause over recoveries		4.8	0.3
Regulatory Assets, Current		48.7	18.5
Regulatory Assets, Noncurrent		306	285.8
Regulatory Liability, Current		29	36.6
Regulatory Liability, Noncurrent		1,223.5	1,270.7
Other Regulatory Liabilities [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	[1]	6.9	1.4
Regulatory Liability, Noncurrent		5.8	6.8
Accrued removal obligations [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Noncurrent		318.5	308.1
Pension tracker [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Noncurrent		0	18.7
Oklahoma demand program rider under recovery [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	[2]	0	6.4
Other Regulatory Assets [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	[2]	7.5	3.2
Regulatory Assets, Noncurrent		13.4	12.8
Benefit Obligations [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		167.2	188.2
Smart Grid [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		18.4	25.6
Deferred storm expenses [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		65.5	36.5
Unamortized loss on reacquired debt [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Noncurrent		$ 10.6	$ 11.4
[1]	Included in Other Current Liabilities in the Balance Sheets.
[2]	Included in Other Current Assets in the Balance Sheets.

Summary of Significant Accoun_7

Summary of Significant Accounting Policies Accounting Records (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets, Current		$ 48.7	$ 18.5
Regulatory Assets, Noncurrent		306	285.8
Regulatory Liability, Noncurrent		1,223.5	1,270.7
Components of Benefit Obligation Regulatory Asset		167.2	188.2
Deferred Storm and Property Reserve Deficiency, Current		2.7
Regulatory Liability, Current		29	36.6
Deferred Pension Expenses [Member]
Regulatory Assets, Noncurrent		8	6.8
Production Tax Credit Rider [Member]
Regulatory Assets, Current	[1]	1.7	6.9
Dry Scrubber Regulatory Asset [Member]
Regulatory Assets, Noncurrent		20.6	4.5
Regulatory Asset [Member]
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year		8.1
Pension tracker [Member]
Regulatory Assets, Noncurrent		2.3	0
Pension Plans [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset		160.5	185.3
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year		11.4
Other Postretirement Benefit Plans, Defined Benefit [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset		23.3	25.6
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year		2.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Prior Service Cost [Member]
Components of Benefit Obligation Regulatory Asset		(16.6)	(22.7)
Components of Net Periodic Benefit Costs to be Recognized in Next Fiscal Year		(6.1)
Reserve for Tax Refund [Member]
Regulatory Liability, Current	[2]	12.7	15.4
Transmission Cost Recovery Rider [Member]
Regulatory Liability, Current	[2]	0	2.7
Income taxes recoverable from customers, net [Member]
Regulatory Liability, Noncurrent		899.2	937.1
SPP Cost Tracker Rider Over Recovery [Member]
Regulatory Liability, Current	[2]	2.6	16.8
Other Regulatory Liabilities [Member]
Regulatory Liability, Noncurrent		5.8	6.8
Regulatory Liability, Current	[2]	6.9	1.4
Oklahoma demand program rider over recovery [Member]
Regulatory Liability, Current	[2]	$ 2	$ 0
[1]	Included in Other Current Assets in the Balance Sheets.
[2]	Included in Other Current Liabilities in the Balance Sheets.

Summary of Significant Accoun_8

Summary of Significant Accounting Policies Allowance for Uncollectible Accounts Receviable (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable reserve	$ 1.5	$ 1.7

Summary of Significant Accoun_9

Summary of Significant Accounting Policies Fuel Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Other	$ 19.6	$ 25.5
Fuel inventories	46.3	57.6
Other Liabilities, Noncurrent	170.6	137.8
Public Utilities, Inventory, Fuel [Member]
Fuel inventories	$ 46.3	$ 57.6

Summary of Significant Accou_10

Summary of Significant Accounting Policies Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 12,906.6		$ 12,365.1
Accumulated Depreciation	3,868.1		3,727.4
Property, Plant and Equipment, Net	9,038.5		8,637.7
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments, Related Accumulated Depreciation	61.8		56.3
OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	12,906.6		12,365.1
Accumulated Depreciation	3,868.1		3,727.4
Property, Plant and Equipment, Net	9,038.5		8,637.7
Capitalized Computer Software, Gross	71.3		44.3
Capitalized Computer Software, Amortization	11		9.6		$ 8.8
Electric Distribution [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,468.6		4,229.4
Accumulated Depreciation	1,381.1		1,324.5
Property, Plant and Equipment, Net	3,087.5		2,904.9
Electric Generation Equipment [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,838.6	[1]	4,657.2	[2]
Accumulated Depreciation	1,601	[1]	1,572.8	[2]
Property, Plant and Equipment, Net	3,237.6	[1]	3,084.4	[2]
Amount of Acquisition Adjustments	148.3		148.3
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments, Related Accumulated Depreciation	61.8		56.3
Electric Transmission [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,901.1	[3]	2,846.7	[4]
Accumulated Depreciation	565.5	[3]	534.2	[4]
Property, Plant and Equipment, Net	2,335.6	[3]	2,312.5	[4]
Amount of Acquisition Adjustments	3.3		3.3
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments, Related Accumulated Depreciation	0.8		0.7
Finite-Lived Intangible Assets, Major Class Name [Domain] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	225.2		187.6
Accumulated Depreciation	145.4		135.1
Property, Plant and Equipment, Net	79.8		52.5
Property, Plant and Equipment, Other Types [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	473.1		444.2
Accumulated Depreciation	175.1		160.8
Property, Plant and Equipment, Net	$ 298		$ 283.4
McClain Plant [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	77.00%	[5]	77.00%	[6]
Property, Plant and Equipment, Gross	$ 254.4	[5]	$ 227.2	[6]
Accumulated Depreciation	83.5	[5]	78.2	[6]
Property, Plant and Equipment, Net	170.9	[5]	149	[6]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0.2		$ 0.2
Redbud Plant [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	51.00%	[5],[7]	51.00%	[6],[8]
Property, Plant and Equipment, Gross	$ 529.9	[5],[7]	$ 493.9	[6],[8]
Accumulated Depreciation	159	[5],[7]	145.3	[6],[8]
Property, Plant and Equipment, Net	370.9	[5],[7]	348.6	[6],[8]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	1.4		0.9
Amount of Acquisition Adjustments	$ 148.3		$ 148.3
[1]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million.
[2]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $56.3 million.
[3]	This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.8 million.
[4]	This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.7 million.
[5]	Construction work in progress was $0.2 million and $1.4 million for the McClain and Redbud Plants, respectively.
[6]	Construction work in progress was $0.2 million and $0.9 million for the McClain and Redbud Plants, respectively.
[7]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $61.8 million.
[8]	This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $56.3 million.

Summary of Significant Accou_11

Summary of Significant Accounting Policies Depreciation and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Provision for Depreciation Rate	2.70%	2.70%
Projected Provision for Depreciation in Next Fiscal Year	2.70%
Percent Of Intangible Plant Balance Amortizable	98.90%
Percent of Intangible Plant Balance Amortizable Thereafter	1.10%
Transmission Equipment [Member] | OG&E [Member]
Amount of Acquisition Adjustments	$ 3.3
Redbud Plant [Member]
Amount of Acquisition Adjustments	$ 148.3	$ 148.3

Summary of Significant Accou_12

Summary of Significant Accounting Policies Asset Retirement Obligations (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at January 1		$ 83.9	$ 75.1
Accretion expense		1	3.4
Revisions in estimated cash flows	[1]	(2.4)	6.8
Liabilities settled	[2]	(9)	(1.4)
Balance at December 31		$ 73.5	$ 83.9
[1]	Assumptions changed related to the estimated cost of the removal of wind turbine assets and asbestos removal at OG&E's generating facilities.
[2]	Asset retirement obligations were settled for asbestos removal and for the closure of an ash pond at OG&E's generating facilities.

Summary of Significant Accou_13

Summary of Significant Accounting Policies Environmental Costs (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Site Contingency [Line Items]
Accrued Environmental Loss Contingencies, Noncurrent	$ 18.7	$ 23.4

Summary of Significant Accou_14

Summary of Significant Accounting Policies Allowance for Funds Used During Construction (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018
Public Utilities, Allowance for Funds Used During Construction, Rate	8.20%	7.60%	7.60%

Accounting Pronouncement (Detai

Accounting Pronouncement (Details) - USD ($) $ in Millions	Dec. 31, 2019		Jan. 01, 2019
Accounting Pronouncement Details [Abstract]
Operating Lease, Right-of-Use Asset	$ 39.6	[1]	$ 32.3
Operating Lease, Liability	$ 44.3	[2]	$ 36.9
[1]	Included in Property, Plant and Equipment in the 2019 Balance Sheet.
[2]	Included in Other Deferred Credits and Other Liabilities in the 2019 Balance Sheet.

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,175.5	$ 2,211.7	$ 0
Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	865.8	877.8
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	486.6	500
Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	217.8	228.9
Oilfield [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	200.4	190.4
Public Authority [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	190.3	197.4
Total Retail Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,960.9	1,994.5
Provision for Rate Refund [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(0.9)	(6)
Integrated Market [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	38.4	48.7
Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	148	147.4
Other Contracts with Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 29.1	$ 27.1

Related-Party Transactions Re_3

Related-Party Transactions Related-Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Dividends, Common Stock		$ 185	$ 105
Operating Costs Charged [Member] | OG&E [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	$ 149.8	140.9	134.4
OG&E [Member] | Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	15.9	16.3	14
OG&E [Member] | Natural Gas Transportation [Member] | Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	41.2	37.9	35
OG&E [Member] | Natural Gas Purchases [Member] | Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	(6)	(3.2)	(2.1)
Retained Earnings [Member]
Related Party Transaction [Line Items]
Dividends, Common Stock	$ 0	$ 185	$ 105

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	$ 3,195.2	$ 3,146.9
OG&E Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	3,050.3	3,001.9
Long-term Debt, Fair Value	3,500.4	3,178.2
OG&E Industrial Authority Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	135.4	135.4
Long-term Debt, Fair Value	135.4	135.4
OG&E Tinker Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Amount	9.5	9.6
Long-term Debt, Fair Value	10	8.7
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ 0	$ 0

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2019	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized			7,400,000
Income tax benefit			$ 1.3		$ 1.2	$ 1.2
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Minimum payout range			0.00%
Maximum payout range			200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total Compensation Cost Not yet Recognized			$ 4
Total Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 47		$ 36.86	$ 41.76
Expected Dividend Rate			4.00%		3.60%	3.80%
Expected Volatility Rate			17.00%		19.00%	19.80%
Risk Free Interest Rate			2.47%		2.38%	1.46%
Expected Term			2 years 10 months 9 days		2 years 10 months 9 days	2 years 10 months 9 days
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			227,679		261,423
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			68,396	[1]	91,940	85,501
Equity Instruments Other than Options, Converted in Period	[2]		(95,593)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			(10,360)
Equity Other Than Options, Employee Migration	[3]		3,813
Awards Other than Options, Fully Vested, Outstanding			77,799
Equity Instruments Other than Options, Converted, Aggregrate Intrinsic Value			$ 7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding			12.2
Equity Instruments Other than Options, Fully Vested, Aggregrate Intrinsic Value			$ 4
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Beginning Balance		165,830	165,830
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			68,396	[1]	91,940	85,501
Equity Instruments Other than Options, Vested in Period			(77,799)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			(10,360)
Equity Other Than Options, Employee Migration	[3]		3,813
Equity Instruments Other than Options, Nonvested, Ending Balance			149,880		165,830
Awards Other than Options, Vested and Expected to Vest	[4]		145,790
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value			$ 41.31		$ 39.17
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			47		$ 36.86	$ 41.76
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value			41.76
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value			41.33
Equity Other Than Options, Employee Migration, Weighted Average Grant Date Fair Value			$ 41.43
Equity Instruments Other than Options, Expected to Vest, Intrinsic Value		$ 0
Fair Value of Vested Performance Units and Restricted Stock			$ 3.2		$ 2.1	$ 2.3
Total Compensation Cost Not yet Recognized			$ 3
Total Compensation Cost Not yet Recognized, Period for Recognition			1 year 8 months 4 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested			$ 8.1
Performance Units Related to Earnings Per Share [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 0		$ 31.03	$ 34.83
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			53,977		87,143
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			0		30,649	28,499
Equity Instruments Other than Options, Converted in Period	[2]		(31,865)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			(2,207)
Equity Other Than Options, Employee Migration	[5]		906
Awards Other than Options, Fully Vested, Outstanding			25,931
Equity Instruments Other than Options, Converted, Aggregrate Intrinsic Value			$ 2.5
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding			4
Equity Instruments Other than Options, Fully Vested, Aggregrate Intrinsic Value			$ 2.3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Beginning Balance		55,278	55,278
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			0		30,649	28,499
Equity Instruments Other than Options, Vested in Period			(25,931)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			(2,207)
Equity Other Than Options, Employee Migration	[5]		906
Equity Instruments Other than Options, Nonvested, Ending Balance			28,046		55,278
Awards Other than Options, Vested and Expected to Vest	[4]		28,006
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value			$ 31.03		$ 32.82
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			0		$ 31.03	$ 34.83
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value			34.83
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value			32.02
Equity Other Than Options, Employee Migration, Weighted Average Grant Date Fair Value			$ 32.84
Equity Instruments Other than Options, Expected to Vest, Intrinsic Value		$ 0
Fair Value of Vested Performance Units and Restricted Stock			$ 0.9		$ 1.7	$ 0.4
Total Compensation Cost Not yet Recognized			$ 0.3
Total Compensation Cost Not yet Recognized, Period for Recognition			1 year
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested			$ 1.7
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense			4.5		4.6	3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total Compensation Cost Not yet Recognized			3.3
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense			$ 0.4		$ 0	0
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 41.63
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			25,005		312
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			26,141
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			(1,500)
Equity Other Than Options, Employee Migration	[5]		364
Equity Instruments Other than Options, Vested in Period, Aggregate Intrinsic Value			$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding			$ 1.1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity Instruments Other than Options, Nonvested, Beginning Balance		312	312
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			26,141
Equity Instruments Other than Options, Vested in Period			(312)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			(1,500)
Equity Other Than Options, Employee Migration	[5]		364
Equity Instruments Other than Options, Nonvested, Ending Balance			25,005		312
Awards Other than Options, Vested and Expected to Vest	[4]		20,251
Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value			$ 41.62		$ 31.88
Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			41.63
Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value			31.88
Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value			41.78
Equity Other Than Options, Employee Migration, Weighted Average Grant Date Fair Value			$ 41.78
Fair Value of Vested Performance Units and Restricted Stock			$ 0		$ 0	0.1
Total Compensation Cost Not yet Recognized			$ 0.7
Total Compensation Cost Not yet Recognized, Period for Recognition			2 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested			$ 0.9
Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense			4.9		4.6	3
Performance Units Related to Earnings Per Share [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense			1.5		1.8	0.5
Total Shareholder Return [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense			$ 3		$ 2.8	$ 2.5
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			164,794		8,599	965
[1]	For performance units, this represents the target number of performance units granted. Actual number of performance units earned, if any, is dependent upon performance and may range from zero percent to 200 percent of the target.
[2]	These amounts represent performance units that vested at December 31, 2018 which were settled in February 2019.
[3]	Due to certain employees transferring between OG&E and OGE Energy.
[4]	The intrinsic value of the performance units based on total shareholder return and earnings per share is $8.1 million and $1.7 million, respectively. The intrinsic value of restricted stock units is $0.9 million.
[5]	Due to certain employees transferring between OG&E and OGE Energy.

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Regulatory Liability, Noncurrent		$ 1,223.5	$ 1,270.7
Current Federal Tax Expense (Benefit)		(7.9)	(12.4)	$ 26.3
Current State and Local Tax Expense (Benefit)		4.1	(4.1)	(4.3)
Current Income Tax Expense (Benefit)		(3.8)	(16.5)	22
Deferred Federal Income Tax Expense (Benefit)		37.7	53.7	100
Deferred State and Local Income Tax Expense (Benefit)		(13.8)	2.7	19.9
Deferred Income Tax Expense (Benefit)		23.9	56.4	119.9
Investment Tax Credit		0	0.1	(0.1)
Income Tax Expense (Benefit)		$ 20.1	$ 40	$ 141.8
Statutory federal tax rate		21.00%	21.00%	35.00%
Amortization of net unfunded deferred taxes		(5.60%)	(2.90%)	0.90%
State income taxes, net of federal income tax benefit		(1.80%)	(0.20%)	2.20%
Federal renewable energy credit	[1]	(7.60%)	(6.90%)	(6.10%)
Other		(0.60%)	(0.10%)	(0.30%)
Effective income tax rate		5.40%	10.90%	31.70%
Accelerated depreciation and other property related differences		$ 1,656.8	$ 1,605.3
OG&E Pension Plan		24.5	26
Regulatory assets		28.4	17.4
Income taxes recoverable from customers, net		(229.9)	(239.6)
Bond redemption-unamortized costs		2.2	2.4
Federal tax credits		(238)	(237.5)
State tax credits		(170.8)	(142.3)
Postretirement medical and life insurance benefits		(16)	(16.2)
Net operating losses		(5.7)	(10)
Other		(4.7)	(2.4)
Deferred federal investment tax credits		(4.3)	(6.1)
Accrued vacation		(1.6)	(1.7)
Uncollectible accounts		(0.4)	(0.4)
Total deferred income tax liabilities, net		951.4	892.7
Unrecognized Tax Benefits		20.7	20.7	$ 20.7	$ 20.7
Current year additions		0	0	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		0
Tax Credit Carryforward, Deferred Tax Asset		238	237.5
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Asset Retirement Obligations		19.2	21.5
Non-Current Deferred Tax Assets, Regulatory Liabilities		68.1	78.8
Non-Current Deferred Tax Assets, Deferred Federal Investment Tax Credits		1.8	$ 1.9
State operating loss [Member]
Operating Loss Carryforwards		127.3
Deferred Tax Assets, Operating Loss Carryforwards, State and Local		5.7
Federal tax credits [Member]
Federal tax credits		(238)
Tax Credit Carryforward, Amount		238
Tax Credit Carryforward, Deferred Tax Asset		238
Oklahoma investment tax credits [Member]
State tax credits		130.4
Tax Credit Carryforward, Amount		165.1
Oklahoma capital investment board credits [Member]
State tax credits		12.4
Tax Credit Carryforward, Amount		12.4
Oklahoma zero emission tax credits [Member]
State tax credits		28
Tax Credit Carryforward, Amount		34.9
OG&E [Member]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 16.4		$ 16.4
[1]	Represents credits associated with the production from OG&E's wind farms.

Common Stock and Cumulative P_2

Common Stock and Cumulative Preferred Stock (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Issued During Period, Shares, New Issues	0	0	0

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total long-term debt	$ 3,195.2	$ 3,146.9
Percent of Principal Amount Subject to Optional Tender	100.00%
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Date Due	Mar. 15, 2030
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 0
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Debt Instrument, Face Amount	$ 300
Garfield Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Date Due	Jan. 1, 2025
Muskogee Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Date Due	Jan. 1, 2025
Muskogee Industrial Authority Bond, Due June 1, 2027 [Member]
Debt Instrument [Line Items]
Date Due	Jun. 1, 2027
Redeemable during the next 12 months [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 135.4
OG&E [Member] | Redeemable during the next 12 months [Member] | Garfield Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Long term debt, gross	47	47
OG&E [Member] | Redeemable during the next 12 months [Member] | Muskogee Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Long term debt, gross	32.4	32.4
OG&E [Member] | Redeemable during the next 12 months [Member] | Muskogee Industrial Authority Bond, Due June 1, 2027 [Member]
Debt Instrument [Line Items]
Long term debt, gross	$ 56	$ 56
Minimum [Member] | Redeemable during the next 12 months [Member] | Garfield Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Minimum [Member] | Redeemable during the next 12 months [Member] | Muskogee Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.19%
Minimum [Member] | Redeemable during the next 12 months [Member] | Muskogee Industrial Authority Bond, Due June 1, 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.20%
Maximum [Member] | Redeemable during the next 12 months [Member] | Garfield Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.50%
Maximum [Member] | Redeemable during the next 12 months [Member] | Muskogee Industrial Authority Bond, Due January 1, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.35%
Maximum [Member] | Redeemable during the next 12 months [Member] | Muskogee Industrial Authority Bond, Due June 1, 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.48%

Short-Term Debt and Credit Fa_2

Short-Term Debt and Credit Facility Short-Term Debt and Credit Facility (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Advances to parent	$ 304.8	$ 319.5
Outstanding Intercompany Borrowings	0
OG&E [Member]
Line of Credit Facility [Line Items]
Intercompany Borrowings, Maximum Borrowing Capacity	$ 350
Intercompany Borrowing Agreement, Expiration Date	Mar. 8, 2023
Letters of Credit Outstanding, Amount	$ 0.3
Short-term Debt, Weighted Average Interest Rate, at Point in Time	1.00%
Commercial Paper	$ 0
Short Term Borrowing Capacity That Has Regulatory Approval	$ 800
Period For Which Regulatory Approval Has Been Given to Acquire Short Term Debt	2 years
Ratio of Consolidated Debt to Consolidated Capitalization	65.00%
Uninsured Judgements [Member] | OG&E [Member]
Line of Credit Facility [Line Items]
Acceleration of Indebtedness of Credit Facility	$ 100
Uninsured Judgements [Member] | OGE Energy [Member]
Line of Credit Facility [Line Items]
Acceleration of Indebtedness of Credit Facility	$ 100

Retirement Plans and Postreti_3

Retirement Plans and Postretirement Benefit Plans (Details) - USD ($) $ in Millions		9 Months Ended		12 Months Ended
		Sep. 30, 2019		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions				$ 20		$ 15
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		200.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay		5.00%
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions				20		15
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Effect of One Percentage Point Increase on Service and Interest Cost Components				0		0		$ 0
Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation				0.1		0.1		0.1
Effect of One Percentage Point Decrease on Service and Interest Cost Components				0		0		0
Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation				0.2		0.2		0.2
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months									$ 44.6
Defined Benefit Plan, Expected Future Benefit Payment, Year Two									44.2
Defined Benefit Plan, Expected Future Benefit Payment, Year Three									42.5
Defined Benefit Plan, Expected Future Benefit Payment, Year Four									42.2
Defined Benefit Plan, Expected Future Benefit Payment, Year Five									42
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter									179.8
Defined Contribution Plan, Cost				11		9.8		9.7
Postemployment Benefits Liability									1.7		$ 1.7
Cash [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		$ 0.9		0.9
Fair Value of Plan Assets, Ending						0.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.9		0.9		0.9					0.9
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.9		0.9
Fair Value of Plan Assets, Ending						0.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.9		0.9		0.9					0.9
Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending						0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0					0
Restoration of Retirement Income Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant				0		0
Employer contributions				0.9		0.6
Defined Benefit Plan, Plan Assets, Benefits Paid				0		0
Defined Benefit Plan, Benefit Obligation, Benefits Paid				0		0
Settlement				0.5		0.4		0
Accumulated Benefit Obligation									4.8		5
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		6		6		4.2
Service cost				0.2		0.2		0.1
Interest cost				0.2		0.2		0.2
Plan settlements				0.9		0.6
Participants' contributions				0		0
Actuarial gains (losses)				0.6		2
Benefit Obligation, Ending				6.1		6		4.2
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0		0
Actual return on plans' assets				0		0
Employer contributions				0.9		0.6
Plan settlements				0.9		0.6
Fair Value of Plan Assets, Ending				0		0		0
Funded Status of Plan									(6.1)		(6)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost				0.2		0.2		0.1
Interest cost				0.2		0.2		0.2
Expected return on plan assets				0		0		0
Defined Benefit Plan, Amortization of Gain (Loss)				(0.3)		(0.5)		(0.4)
Amortization of unrecognized prior service cost	[1]			0		0		0
Settlement				0.5		0.4		0
Net Periodic Benefit Cost				1.2		1.3		0.7
Amount Attributable to Unconsolidated Affiliates				0.5		1.2		0
Fair Value of Plan Assets		0		0		0		0	0		0		$ 0
Defined Benefit Plan, Net Periodic Benefit Cost, Net of Unconsolidated Affiliates				1.7		2.5		0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement				(0.5)		(0.4)		0
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant				0		0
Employer contributions				5		5
Defined Benefit Plan, Plan Assets, Benefits Paid				(12.7)		(12.8)
Defined Benefit Plan, Benefit Obligation, Benefits Paid				(12.7)		(12.8)
Settlement				16.4		19.4		11.7
Accumulated Benefit Obligation									425.8		417.6
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		453.6		453.6		510.6
Service cost				9		9.8		10.1
Interest cost				15.6		17.6		19.5
Plan settlements				45.6		52.6
Participants' contributions				0		0
Actuarial gains (losses)				42.1		(19)
Benefit Obligation, Ending				462		453.6		510.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		$ 387.6		387.6		477.2
Actual return on plans' assets				64.8		(29.2)
Employer contributions				5		5
Plan settlements				45.6		52.6
Fair Value of Plan Assets, Ending				399.1		387.6		477.2
Funded Status of Plan									$ (62.9)		$ (66)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost				9		9.8		10.1
Interest cost				15.6		17.6		19.5
Expected return on plan assets				(27.6)		(33.1)		(32.8)
Defined Benefit Plan, Amortization of Gain (Loss)				(12.9)		(12.1)		(13)
Amortization of unrecognized prior service cost	[1]			0		0		0
Settlement				16.4		19.4		11.7
Net Periodic Benefit Cost				26.3		25.8		21.5
Amount Attributable to Unconsolidated Affiliates				4.5		5.7		0
Capitalized Portion of Net Periodic Benefit Cost				$ 3		$ 3.2		$ 3.4
Assumptions Used Calculating Benefit Obligation, Discount Rate									3.15%		4.20%		3.60%
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets				7.50%		7.50%		7.50%
Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase				4.20%		4.20%		4.20%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase									4.20%		4.20%		4.20%
Fair Value of Plan Assets		$ 387.6		$ 387.6		$ 387.6		$ 477.2	$ 399.1		$ 387.6		$ 477.2
Defined Benefit Plan, Net Periodic Benefit Cost, Net of Unconsolidated Affiliates				30.8		31.5		21.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement				(16.4)		(19.4)		(11.7)
Pension Plans [Member] | OKLAHOMA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement	[2]			(17.9)		(22.1)		(13.2)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement	[2]			(17.9)		(22.1)		(13.2)
Additional Pension Expense to Meet State Requirements	[2]			(16.1)		(14.1)		(2.3)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]			17.9		22.1		13.2
Additional Pension Expense to Meet State Requirements	[2]			(16.1)		(14.1)		(2.3)
Pension Plans [Member] | ARKANSAS
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement	[2]			1.7		2.1		1.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement	[2]			1.7		2.1		1.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]			(1.7)		(2.1)		(1.1)
Pension Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Money market funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									7.5	[3]	0.3	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.3		0.3
Fair Value of Plan Assets, Ending				7.5		0.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.3		0.3		0.3			7.5		0.3
Pension Plans [Member] | Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Money market funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | U.S. common stocks [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		169.3		169.3
Fair Value of Plan Assets, Ending				202		169.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		169.3		169.3		169.3			202		169.3
Pension Plans [Member] | U.S. common stocks [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		169.3		169.3
Fair Value of Plan Assets, Ending				202		169.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		169.3		169.3		169.3			202		169.3
Pension Plans [Member] | U.S. common stocks [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | U.S. treasury notes and bonds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3],[5]	0	[4],[6]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[6]	137.9		137.9
Fair Value of Plan Assets, Ending				134.8	[5]	137.9	[6]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		137.9	[6]	137.9	[6]	137.9	[6]		134.8	[5]	137.9	[6]
Pension Plans [Member] | U.S. treasury notes and bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[6]	137.9		137.9
Fair Value of Plan Assets, Ending				134.8	[5]	137.9	[6]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		137.9	[6]	137.9	[6]	137.9	[6]		134.8	[5]	137.9	[6]
Pension Plans [Member] | U.S. treasury notes and bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[6]	0		0
Fair Value of Plan Assets, Ending				0	[5]	0	[6]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0	[6]	0	[6]	0	[6]		0	[5]	0	[6]
Pension Plans [Member] | Mortgage-backed securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		65.9		65.9
Fair Value of Plan Assets, Ending				45.8		65.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		65.9		65.9		65.9			45.8		65.9
Pension Plans [Member] | Mortgage-backed securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Mortgage-backed securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		65.9		65.9
Fair Value of Plan Assets, Ending				45.8		65.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		65.9		65.9		65.9			45.8		65.9
Pension Plans [Member] | Corporate fixed income and other securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		143.2		143.2
Fair Value of Plan Assets, Ending				130.5		143.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		143.2		143.2		143.2			130.5		143.2
Pension Plans [Member] | Corporate fixed income and other securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Corporate fixed income and other securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		143.2		143.2
Fair Value of Plan Assets, Ending				130.5		143.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		143.2		143.2		143.2			130.5		143.2
Pension Plans [Member] | Commingled fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									23.9	[3],[7]	19.7	[4],[8]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[8]	19.7		19.7
Fair Value of Plan Assets, Ending				23.9	[7]	19.7	[8]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		19.7	[8]	19.7	[8]	19.7	[8]		23.9	[7]	19.7	[8]
Pension Plans [Member] | Commingled fund [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[8]	0		0
Fair Value of Plan Assets, Ending				0	[7]	0	[8]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0	[8]	0	[8]	0	[8]		0	[7]	0	[8]
Pension Plans [Member] | Commingled fund [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	[8]	0		0
Fair Value of Plan Assets, Ending				0	[7]	0	[8]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0	[8]	0	[8]	0	[8]		0	[7]	0	[8]
Pension Plans [Member] | Foreign government bonds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		4.4		4.4
Fair Value of Plan Assets, Ending				3		4.4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		4.4		4.4		4.4			3		4.4
Pension Plans [Member] | Foreign government bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Foreign government bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		4.4		4.4
Fair Value of Plan Assets, Ending				3		4.4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		4.4		4.4		4.4			3		4.4
Pension Plans [Member] | U.S. municipal bonds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.6		0.6
Fair Value of Plan Assets, Ending				1.1		0.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.6		0.6		0.6			1.1		0.6
Pension Plans [Member] | U.S. municipal bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | U.S. municipal bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.6		0.6
Fair Value of Plan Assets, Ending				1.1		0.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.6		0.6		0.6			1.1		0.6
Pension Plans [Member] | Mutual fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		8		8
Fair Value of Plan Assets, Ending				2.4		8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		8		8		8			2.4		8
Pension Plans [Member] | Mutual fund [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		8		8
Fair Value of Plan Assets, Ending				2.4		8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		8		8		8			2.4		8
Pension Plans [Member] | Mutual fund [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Treasury futures, receivable [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		27		27
Fair Value of Plan Assets, Ending				22.9		27
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		27		27		27			22.9		27
Pension Plans [Member] | Treasury futures, receivable [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Treasury futures, receivable [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		27		27
Fair Value of Plan Assets, Ending				22.9		27
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		27		27		27			22.9		27
Pension Plans [Member] | Treasury futures, payable [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(20.4)		(20.4)
Fair Value of Plan Assets, Ending				(10.9)		(20.4)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		(20.4)		(20.4)		(20.4)			(10.9)		(20.4)
Pension Plans [Member] | Treasury futures, payable [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Treasury futures, payable [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(20.4)		(20.4)
Fair Value of Plan Assets, Ending				(10.9)		(20.4)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		(20.4)		(20.4)		(20.4)			(10.9)		(20.4)
Pension Plans [Member] | Cash collateral [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.7		0.7
Fair Value of Plan Assets, Ending				0.6		0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.7		0.7		0.7			0.6		0.7
Pension Plans [Member] | Cash collateral [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.7		0.7
Fair Value of Plan Assets, Ending				0.6		0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.7		0.7		0.7			0.6		0.7
Pension Plans [Member] | Cash collateral [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Receivable (foreign currency) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									0	[3]	0	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.1		0.1
Fair Value of Plan Assets, Ending				0.1		0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.1		0.1		0.1			0.1		0.1
Pension Plans [Member] | Receivable (foreign currency) [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Pension Plans [Member] | Receivable (foreign currency) [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0.1		0.1
Fair Value of Plan Assets, Ending				0.1		0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0.1		0.1		0.1			0.1		0.1
Pension Plans [Member] | Preferred stock [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment	[3]								0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Ending				0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets				0.7					0.7
Pension Plans [Member] | Preferred stock [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Ending				0.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets				0.7					0.7
Pension Plans [Member] | Preferred stock [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Ending				0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets				0					0
Pension Plans [Member] | Interest and dividends receivable [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		3		3
Fair Value of Plan Assets, Ending				2.4		3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		3		3		3			2.4		3
Pension Plans [Member] | Payable to broker for securities purchased [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(36.9)		(36.9)
Fair Value of Plan Assets, Ending				(36.5)		(36.9)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		(36.9)		(36.9)		(36.9)			(36.5)		(36.9)
Pension Plans [Member] | Plan investments attributable to affiliates [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		(135.2)		(135.2)
Fair Value of Plan Assets, Ending				(131.2)		(135.2)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		(135.2)		(135.2)		(135.2)			(131.2)		(135.2)
Pension Plans [Member] | Total Plan assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		387.6		387.6
Fair Value of Plan Assets, Ending				399.1		387.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		387.6		387.6		387.6			399.1		387.6
Pension Plans [Member] | Total Plan investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investment									31.4	[3]	20	[4]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		556.7		556.7
Fair Value of Plan Assets, Ending				564.4		556.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		556.7		556.7		556.7			564.4		556.7
Pension Plans [Member] | Total Plan investments [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		315.9		315.9
Fair Value of Plan Assets, Ending				340.5		315.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		315.9		315.9		315.9			340.5		315.9
Pension Plans [Member] | Total Plan investments [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		220.8		220.8
Fair Value of Plan Assets, Ending				192.5		220.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		220.8		220.8		220.8			192.5		220.8
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant				3		2.9
Employer contributions				4.1		4.8
Defined Benefit Plan, Plan Assets, Benefits Paid				(9.8)		(11.8)
Defined Benefit Plan, Benefit Obligation, Benefits Paid				(9.8)		(11.8)
Settlement				0		0		0.4
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning		104.8		104.8		115.8
Service cost				0.2		0.2		0.4
Interest cost				4.3		4.2		5.6
Plan settlements				0		0
Participants' contributions				3		2.9
Actuarial gains (losses)				2.2		(6.5)
Benefit Obligation, Ending				104.7		104.8		115.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		40.6		40.6		45.2
Actual return on plans' assets				4		(0.5)
Employer contributions				4.1		4.8
Plan settlements				0		0
Fair Value of Plan Assets, Ending				41.9		40.6		45.2
Funded Status of Plan									$ (62.8)		$ (64.2)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost				0.2		0.2		0.4
Interest cost				4.3		4.2		5.6
Expected return on plan assets				(1.7)		(1.8)		(2)
Defined Benefit Plan, Amortization of Gain (Loss)				(2.1)		(3.8)		(1.9)
Amortization of unrecognized prior service cost	[1]			(6.1)		(6.1)		(2.5)
Settlement				0		0		0.4
Net Periodic Benefit Cost				(1.2)		0.3		3.8
Amount Attributable to Unconsolidated Affiliates				(0.6)		(0.7)		0
Capitalized Portion of Net Periodic Benefit Cost				$ 0.1		$ 0.1		$ 1.1
Assumptions Used Calculating Benefit Obligation, Discount Rate									3.25%		4.30%		3.70%
Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets				4.00%		4.00%		4.00%
Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase								4.20%
Health Care Cost Trend Rate Assumed for Next Fiscal Year											7.00%
Fair Value of Plan Assets		40.6		$ 41.9		$ 45.2		$ 45.2	$ 41.9		$ 40.6		$ 45.2
Defined Benefit Plan, Net Periodic Benefit Cost, Net of Unconsolidated Affiliates				(1.8)		(0.4)		3.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement				0		0		(0.4)
Other Postretirement Benefit Plans, Defined Benefit [Member] | OKLAHOMA
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Additional Pension Expense to Meet State Requirements	[2]			1		4.4		6.2
Additional Pension Expense to Meet State Requirements	[2]			1		4.4		$ 6.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		9.8		9.8
Fair Value of Plan Assets, Ending				12.1		9.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		9.8		9.8		9.8			12.1		9.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		0		0
Fair Value of Plan Assets, Ending				0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		0		0		0			0		0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		36		36
Fair Value of Plan Assets, Ending				34.8		36
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		36		36		36			34.8		36
Other Postretirement Benefit Plans, Defined Benefit [Member] | Money market funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Ending				1.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets				1.2					1.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Ending				1.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets				1.2					1.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Money market funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Ending				0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets				0					0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Total Plan investments [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		45.8		45.8
Fair Value of Plan Assets, Ending				46.9		45.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		45.8		$ 45.8		45.8			$ 46.9		45.8
Less Than 90% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				50.00%
Projected Benefit Obligation Funded Status Thresholds Equity				50.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
95% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				58.00%
Projected Benefit Obligation Funded Status Thresholds Equity				42.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
100% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				65.00%
Projected Benefit Obligation Funded Status Thresholds Equity				35.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
105% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				73.00%
Projected Benefit Obligation Funded Status Thresholds Equity				27.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
110% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				80.00%
Projected Benefit Obligation Funded Status Thresholds Equity				20.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
115% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				85.00%
Projected Benefit Obligation Funded Status Thresholds Equity				15.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
120% [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Projected Benefit Obligation Funded Status Thresholds Fixed Income				90.00%
Projected Benefit Obligation Funded Status Thresholds Equity				10.00%
Projected Benefit Obligation Funded Status Thresholds				100.00%
Domestic All-Cap/Large Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									40.00%
Domestic Mid-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									15.00%
Domestic Small-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									25.00%
International Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									20.00%
OG&E [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		5		$ 5		5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions		5		5		5
OG&E [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning		40.6		40.6
Fair Value of Plan Assets, Ending				41.9		40.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Fair Value of Plan Assets		$ 40.6		$ 40.6		$ 40.6			$ 41.9		$ 40.6
Minimum [Member] | Domestic All-Cap/Large Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									35.00%
Minimum [Member] | Domestic Mid-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									5.00%
Minimum [Member] | Domestic Small-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									5.00%
Minimum [Member] | International Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									10.00%
Maximum [Member] | Domestic All-Cap/Large Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									60.00%
Maximum [Member] | Domestic Mid-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									25.00%
Maximum [Member] | Domestic Small-Cap Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									30.00%
Maximum [Member] | International Equity [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Target Plan Asset Allocations									30.00%
[1]	Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment.
[2]	Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.
[3]	(A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[4]	GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[5]	This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher.
[6]	This category represents U.S. Treasury notes and bonds with a Moody's Investors Service rating of Aaa and Government Agency Bonds with a Moody's Investors Service rating of A1 or higher.
[7]	This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.
[8]	This category represents units of participation in a commingled fund that primarily invested in stocks of international companies and emerging markets.

Retirement Plans and Postreti_4

Retirement Plans and Postretirement Benefit Plans Postretirement Benefit Plans (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2019	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Level 3 Asset Value, Beginning of Period		$ 36	$ 36
Interest income			0.8
Dividend income			0.5
Unrealized gains			1.4
Administrative expenses and charges			(0.1)
Claims paid			(3.8)
Level 3 Asset Value, End of Period			34.8		$ 36
Postretirement Plan, Expected Future Benefit Payments in Year One			8.9
Postretirement Plan, Expected Future Benefit Payments in Year Two			8.9
Postretirement Plan, Expected Future Benefit Payments in Year Three			8.8
Postretirement Plan, Expected Future Benefit Payments in Year Four			7.4
Postretirement Plan, Expected Future Benefit Payments in Year Five			7.3
Postretirement Plan, Expected Future Benefit Payments Thereafter			32.4
Postemployment Benefits Liability			$ 1.7		1.7
Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets					0.9
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets					0.9
Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets					$ 0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate			4.30%		3.70%		4.20%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year					7.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets			4.00%		4.00%		4.00%
Plan settlements			$ 0		$ 0
Benefit Obligation			104.7		104.8		$ 115.8
Fair Value of Plan Assets			41.9		40.6		45.2
Funded Status of Plan			(62.8)		(64.2)
Plan investments attributable to affiliates			(5)		(5.2)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			0		0		(0.4)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			(1.2)		0.3		$ 3.8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase							4.20%
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			12.1		9.8
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			0		0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			34.8		36
Other Postretirement Benefit Plans, Defined Benefit [Member] | Group Retiree Medical Insurance Contract [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			34.8		36
Other Postretirement Benefit Plans, Defined Benefit [Member] | Group Retiree Medical Insurance Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			0		0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Group Retiree Medical Insurance Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			34.8		36
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Equity Mutual Funds Investment [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			10.9		8.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Equity Mutual Funds Investment [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			10.9		8.9
Other Postretirement Benefit Plans, Defined Benefit [Member] | U.S. Equity Mutual Funds Investment [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			0		$ 0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Money market funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			1.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			1.2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Money market funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			$ 0
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate			3.63%		3.73%		4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets			7.50%		7.50%		7.50%
Plan settlements			$ 45.6		$ 52.6
Benefit Obligation			462		453.6		$ 510.6
Fair Value of Plan Assets			399.1		387.6		477.2
Funded Status of Plan			(62.9)		(66)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			(16.4)		(19.4)		(11.7)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			$ 26.3		$ 25.8		$ 21.5
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase			4.20%		4.20%		4.20%
Pension Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			$ 0		$ 0
Pension Plans [Member] | Money market funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			7.5		0.3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Alternative Investment			7.5	[1]	0.3	[2]
Pension Plans [Member] | Money market funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			0		0
Pension Plans [Member] | Money market funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			0		0
Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan settlements			0.9		0.6
Benefit Obligation			6.1		6		$ 4.2
Fair Value of Plan Assets			0		0		0
Funded Status of Plan			(6.1)		(6)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			(0.5)		(0.4)		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			1.2		1.3		0.7
OG&E [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets			41.9		40.6
ARKANSAS | Pension Plans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[3]		$ (1.7)		$ (2.1)		$ (1.1)
[1]	(A) GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[2]	GAAP allows the measurement of certain investments that do not have a readily determinable fair value at the net asset value. These investments do not consider the observability of inputs; therefore, they are not included within the fair value hierarchy.
[3]	Included in the pension regulatory asset or liability in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions		12 Months Ended
		Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months		$ 141.1
Operating Leases, Future Minimum Payments, Due in Two Years		113.5
Operating Leases, Future Minimum Payments, Due in Three Years		109.2
Operating Leases, Future Minimum Payments, Due in Four Years		121
Operating Leases, Future Minimum Payments, Due in Five Years		122.5
Operating Leases, Future Minimum Payments Due		607.3
Utilities Operating Expense, Purchased Power under Long-term Contracts		57.7	$ 57.6	$ 61.1
Other Commitments [Line Items]
Operating Leases, Future Minimum Payments Due		607.3
Operating Leases, Future Minimum Payments Due, Next Twelve Months		141.1
Operating Leases, Future Minimum Payments, Due in Two Years		113.5
Operating Leases, Future Minimum Payments, Due in Three Years		109.2
Operating Leases, Future Minimum Payments, Due in Four Years		121
Operating Leases, Future Minimum Payments, Due in Five Years		122.5
OG&E minimum fuel purchase commitments [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		271.4
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months		82.6
Unrecorded Unconditional Purchase Obligation, Due within Two Years		55.1
Unrecorded Unconditional Purchase Obligation, Due within Three Years		50.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years		50.4
Unrecorded Unconditional Purchase Obligation, Due within Five Years		32.9
Other Commitments [Line Items]
Operating Leases, Future Minimum Payments Due		271.4
Unrecorded Unconditional Purchase Obligation, Due within Five Years		32.9
OG&E long-term service agreement commitments [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		53.1
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months		2.4
Unrecorded Unconditional Purchase Obligation, Due within Two Years		2.4
Unrecorded Unconditional Purchase Obligation, Due within Three Years		2.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years		13.8
Unrecorded Unconditional Purchase Obligation, Due within Five Years		32.1
Other Commitments [Line Items]
Operating Leases, Future Minimum Payments Due		53.1
Unrecorded Unconditional Purchase Obligation, Due within Five Years		32.1
OG&E total cogeneration payments [Member]
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Amount		14.7	112.4	115.2
OG&E capacity payments [Member]
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Amount		7.4	60	63
CPV Keenan [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts		27.2	27	29
Edison Mission Energy [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts		23.1	21.7	22.1
FPL Energy [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts	[1]	0	2.1	2.6
NextEra Energy [Member]
Loss Contingencies [Line Items]
Utilities Operating Expense, Purchased Power under Long-term Contracts		7.4	$ 6.8	$ 7.4
OG&E expected wind purchase commitments [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		282.4
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months		55.7
Unrecorded Unconditional Purchase Obligation, Due within Two Years		56
Unrecorded Unconditional Purchase Obligation, Due within Three Years		56.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years		56.8
Unrecorded Unconditional Purchase Obligation, Due within Five Years		57.5
Other Commitments [Line Items]
Operating Leases, Future Minimum Payments Due		282.4
Unrecorded Unconditional Purchase Obligation, Due within Five Years		57.5
Environmental Compliance Plan [Member]
Loss Contingencies [Line Items]
Operating Leases, Future Minimum Payments Due		0.4
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months		0.4
Unrecorded Unconditional Purchase Obligation, Due within Two Years		0
Unrecorded Unconditional Purchase Obligation, Due within Three Years		0
Unrecorded Unconditional Purchase Obligation, Due within Four Years		0
Unrecorded Unconditional Purchase Obligation, Due within Five Years		0
Other Commitments [Line Items]
Operating Leases, Future Minimum Payments Due		0.4
Unrecorded Unconditional Purchase Obligation, Due within Five Years		$ 0
OG&E long-term service agreement commitments [Member] | McClain Plant [Member]
Loss Contingencies [Line Items]
Factored-Fired Hours		128,000
Factored-Fired Starts		4,800
OG&E long-term service agreement commitments [Member] | Redbud Plant [Member]
Loss Contingencies [Line Items]
Additional Factored-Fired Hours		24,000
Factored-Fired Hours		144,000
Factored-Fired Starts		4,500
[1]	OG&E's purchased power contract with FPL Energy for 50 MWs expired in 2018.

Rate Matters and Regulation (De

Rate Matters and Regulation (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets, Current		$ 48.7	$ 18.5
Customer Refund Liability, Current		4.8	0.3
Public Utilities, Amount Requested for Acquisition		53.5
Estimated Refund to SPP		13
Investment in Grid Enhancement		800
Impact to Company [Member]
Estimated Refund to SPP		5
Customer Impact [Member]
Estimated Refund to SPP		$ 8
Oklahoma Corporation Commission [Member]
OG&E's Jurisdictional Revenues		86.00%
Arkansas Public Service Commission [Member]
OG&E's Jurisdictional Revenues		8.00%
Federal Energy Regulatory Commission [Member]
OG&E's Jurisdictional Revenues		6.00%
OKLAHOMA
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 77.6
ARKANSAS
Public Utilities, Requested Rate Increase (Decrease), Amount		5.2
Public Utilities, Approved Rate Increase (Decrease), Amount		(3.3)
Oklahoma demand program rider under recovery [Member]
Regulatory Assets, Current	[1]	$ 0	$ 6.4
FERC [Member]
Recommended Common Equity Percentage		7.85%
Public Utilities, Approved Return on Equity, Percentage		10.60%
[1]	Included in Other Current Assets in the Balance Sheets.

Quarterly Financial Data (Detai

Quarterly Financial Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues	$ 472.5	$ 755.4	$ 513.7	$ 490	$ 511.8	$ 698.8	$ 567	$ 492.7	$ 2,231.6	$ 2,270.3	$ 2,261.1
Operating income	71.8	275	110.6	50.3	58.5	230.3	138.3	67.1	507.7	494.2	528
Net income	$ 28.9	$ 227.2	$ 74.5	$ 19.6	$ 20.8	$ 183.9	$ 92	$ 31.3	$ 350.2	$ 328	$ 305.5

Schedule II (Details)

Schedule II (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Beginning Balance		$ 1.7	$ 1.5	$ 1.5
Valuation Allowances and Reserves, Charged to Cost and Expense		2.2	3.4	2.6
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	[1]	2.4	3.2	2.6
Valuation Allowances and Reserves, Ending Balance		$ 1.5	$ 1.7	$ 1.5
[1]	Uncollectible accounts receivable written off, net of recoveries.

Leases, Codification Topic 84_2

Leases, Codification Topic 842 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	Jan. 01, 2019
Leases [Abstract]
Lessee, Operating Lease, Contingent Liability	$ 6.8		$ 16.2
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	5.1		4.1		$ 5.4
Cash Paid on Operating Leases	4.8
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	10.7
Operating Lease, Right-of-Use Asset	39.6	[1]				$ 32.3
Operating Lease, Liability	$ 44.3	[2]				$ 36.9
Operating Lease, Weighted Average Remaining Lease Term	13 years 6 months
Operating Lease, Weighted Average Discount Rate, Percent	3.90%
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 0		21.1	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	5.3		2.9	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due Year Two	5.2		2.9	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due Year Three	5.2		2.9	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due Year Four	5.2		2.9	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due Year Five	3.1		3	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due after Year Five	34.7		34.6	[3],[4]
Lessee, Operating Lease, Liability, Payments, Due	58.7		70.3	[3],[4]
Lessee, Operating Lease, Contingent Liability	6.8		$ 16.2
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	$ 14.4
[1]	Included in Property, Plant and Equipment in the 2019 Balance Sheet.
[2]	Included in Other Deferred Credits and Other Liabilities in the 2019 Balance Sheet.
[3]	Amounts included for comparability and accounted for in accordance with ASC 840, "Leases."
[4]	At the end of the railcar lease term, which was February 1, 2019, OG&E had the option to either purchase the railcars at a stipulated fair market value or renew the lease. OG&E renewed the lease effective February 1, 2019. If OG&E chose not to purchase the railcars or renew the lease agreement and the actual fair value of the railcars was less than the stipulated fair market value, OG&E would have been responsible for the difference in those values up to a maximum of $16.2 million.