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	0.0	(250.0)
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	$ 0.0	250.0
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	$ 125.0	125.0
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	$ 100.0	100.0
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	$ 400.0	400.0
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	$ 110.0	110.0
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	$ 200.0	200.0
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	$ 250.0	250.0
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	$ 250.0	250.0
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	$ 250.0	250.0
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	$ 250.0	250.0
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	$ 250.0	250.0
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	$ 300.0	300.0
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	$ 300.0	300.0
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	0.0
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	47.0	47.0
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	$ 56.0	$ 56.0

Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.

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Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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