Fair Value Measurements Carrying and Fair Value Amounts (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Commodity Contract [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Energy Derivative Contract Assets	$ 2.1	$ 2.2
Energy Derivative Contracts Liabilities	7.0	16.8
Commodity Contract [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Energy Derivative Contract Assets	2.1	2.2
Energy Derivative Contracts Liabilities	7.0	16.8
OG&E Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	1,903.8	1,655.0
Long-Term Debt, Fair Value	2,362.8	1,831.5
OGE Energy Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	99.6	99.7
Long-Term Debt, Fair Value	109.7	106.4
OG&E Industrial Authority Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	135.4	135.4
Long-Term Debt, Fair Value	135.4	135.4
Enogex LLC Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	448.1	447.8
Long-Term Debt, Fair Value	502.7	480.7
Enogex LLC Revolving Credit Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	0	25.0
Long-Term Debt, Fair Value	$ 0	$ 25.0