Common Equity Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]
Net Income Attributable to OGE Energy	$ 215.2	$ 185.5	$ 330.0	$ 316.5
Basic average common shares outstanding	198.4	197.4	198.1	197.0
Contingently issuable shares (performance units)	1.3	0.9	1.2	0.9
Diluted average common shares outstanding	199.7	198.3	199.3	197.9
Earnings Per Share, Basic and Diluted [Abstract]
Basic Earnings Per Average Common Share Attributable to OGE Energy Common Shareholders	$ 1.08	$ 0.94	$ 1.67	$ 1.61
Diluted Earnings Per Average Common Share Attributable to OGE Energy Common Shareholders	$ 1.08	$ 0.94	$ 1.66	$ 1.60
Anti-dilutive shares excluded from earnings per share calculation	0	0	0	0