Fair Value Measurements Carrying and Fair Value Amounts (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
OG&E Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	$ 1,904.3	$ 1,904.2
Long-Term Debt, Fair Value	2,368.3	2,401.6
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
OG&E Tinker Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	10.6	10.7
Long-Term Debt, Fair Value	10.3	10.0
OGE Energy Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	99.9	99.9
Long-Term Debt, Fair Value	105.6	106.3
Enogex LLC Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	448.5	448.4
Long-Term Debt, Fair Value	492.1	493.4
Enogex LLC Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	250.0	250.0
Long-Term Debt, Fair Value	250.0	250.0
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Energy Derivative Contract Assets	0.4	0.5
Energy Derivative Contracts Liabilities	0.4	0.3
Estimate of Fair Value, Fair Value Disclosure [Member] | Commodity Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Energy Derivative Contract Assets	0.4	0.5
Energy Derivative Contracts Liabilities	$ 0.4	$ 0.3