Common Equity Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Equity [Abstract]
Net Income Attributable to OGE Energy	$ 100.8	$ 91.7	$ 150.1	$ 114.8
Basic average common shares outstanding	199.2	198.3	199.0	198.0
Contingently issuable shares (performance units)	0.8	1.1	0.8	1.1
Diluted average common shares outstanding	200.0	199.4	199.8	199.1
Earnings Per Share, Basic and Diluted [Abstract]
Basic Earnings Per Average Common Share Attributable to OGE Energy Common Shareholders	$ 0.51	$ 0.46	$ 0.75	$ 0.58
Diluted Earnings Per Average Common Share Attributable to OGE Energy Common Shareholders	$ 0.50	$ 0.46	$ 0.75	$ 0.58
Anti-dilutive shares excluded from earnings per share calculation	0	0	0	0

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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