Common Equity Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	300	0	0
Net income attributable to OGE Energy	$ (173.7)	$ 433.6	$ 425.5
Basic Average Common Shares Outstanding	200,100	200,100	199,700
Contingently Issuable Shares (Performance and Restricted Stock Units)	0	600	800
Diluted Average Common Shares Outstanding	200,100	200,700	200,500
Earnings Per Share, Basic and Diluted [Abstract]
Basic earnings per average common share attributable to OGE Energy common shareholders	$ (0.87)	$ 2.17	$ 2.13
Diluted earnings per average common share attributable to OGE Energy common shareholders	$ (0.87)	$ 2.16	$ 2.12
Og and E [Member]
Stock Issued During Period, Shares, New Issues	0	0	0
Retained Earnings [Member]
Net income attributable to OGE Energy	$ (173.7)	$ 433.6	$ 425.5