Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Operating revenues	$ 447.1		$ 719.8		$ 549.9		$ 480.1		$ 526.2		$ 754.7		$ 611.8		$ 560.4		$ 2,196.9		$ 2,453.1		$ 2,867.7
Operating income	46.8		250.8		127.2		56.4		85.1		248.1		141.8		61.8		481.2		536.8		553.5
Net income	$ 29.4		$ 111.2		$ 87.5		$ 43.2		$ 58.4		$ 187.3		$ 100.8		$ 49.3		$ 271.3		$ 395.8		$ 393.8
Basic earnings per average common share attributable to OGE Energy common shareholders	$ 0.15	[1]	$ 0.55	[1]	$ 0.44	[1]	$ 0.22	[1]	$ 0.29	[1]	$ 0.94	[1]	$ 0.51	[1]	$ 0.25	[1]	$ 1.36	[1]	$ 1.99	[1]	$ 1.96
Diluted earnings per average common share attributable to OGE Energy common shareholders	$ 0.15	[1]	$ 0.55	[1]	$ 0.44	[1]	$ 0.22	[1]	$ 0.29	[1]	$ 0.94	[1]	$ 0.50	[1]	$ 0.25	[1]	$ 1.36	[1]	$ 1.98	[1]	$ 1.94

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