Quarterly Financial Data (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Operating revenues	$ 862.1		$ 1,113.4		$ 855.0		$ 840.7		$ 885.2		$ 1,212.1		$ 978.1		$ 840.5		$ 3,671.2		$ 3,915.9		$ 3,716.9
Operating income	97.3		304.0		177.3		98.3		96.9		299.7		182.2		67.9		676.9		646.7		593.9
Net income	43.5		192.4		101.6		47.5		43.2		181.4		109.3		29.7		385.0		363.6		300.4
Net income attributable to OGE Energy	$ 38.5		$ 185.5		$ 93.9		$ 37.1		$ 36.4		$ 178.7		$ 103.0		$ 24.8		$ 355.0		$ 342.9		$ 295.3
Basic earnings per average common share attributable to OGE Energy common shareholders	$ 0.39	[1]	$ 1.88	[1]	$ 0.95	[1]	$ 0.38	[1]	$ 0.37	[1]	$ 1.82	[1]	$ 1.05	[1]	$ 0.25	[1]	$ 3.60	[1]	$ 3.50	[1]	$ 3.03
Diluted earnings per average common share attributable to OGE Energy common shareholders	$ 0.39	[1]	$ 1.87	[1]	$ 0.95	[1]	$ 0.38	[1]	$ 0.37	[1]	$ 1.80	[1]	$ 1.04	[1]	$ 0.25	[1]	$ 3.58	[1]	$ 3.45	[1]	$ 2.99

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