Common Equity Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	0.0		0.0		0.0
Net income attributable to OGE Energy	$ 35.4		$ 250.9		$ 100.2		$ 47.1		$ 54.7		$ 205.1		$ 110.7		$ 55.0		$ 433.6		$ 425.5		$ 619.0
Basic Average Common Shares Outstanding																	200.1		199.7		199.7
Contingently Issuable Shares (Performance and Restricted Stock Units)																	0.6		0.8		0.3
Diluted Average Common Shares Outstanding																	200.7		200.5		200.0
Earnings Per Share, Basic and Diluted [Abstract]
Basic earnings per average common share attributable to OGE Energy common shareholders	$ 0.18	[1]	$ 1.25	[1]	$ 0.50	[1]	$ 0.24	[1]	$ 0.27	[1]	$ 1.03	[1]	$ 0.55	[1]	$ 0.28	[1]	$ 2.17	[1]	$ 2.13	[1]	$ 3.10
Diluted earnings per average common share attributable to OGE Energy common shareholders	$ 0.18	[1]	$ 1.25	[1]	$ 0.50	[1]	$ 0.24	[1]	$ 0.27	[1]	$ 1.02	[1]	$ 0.55	[1]	$ 0.27	[1]	$ 2.16	[1]	$ 2.12	[1]	$ 3.10
Retained Earnings [Member]
Net income attributable to OGE Energy																	$ 433.6		$ 425.5		$ 619.0

[1] Due to the impact of dilution on the earnings per share calculation, quarterly earnings per share amounts may not add to the total.