Fair Value Measurements Carrying and Fair Value Amounts (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	$ 2,848.6		$ 2,737.1
OG&E Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	1,904.2		1,903.8
Long-Term Debt, Fair Value	2,401.6		2,383.8
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	10.7	[1]	0	[1]
Long-Term Debt, Fair Value	10.0	[1]	0	[1]
OGE Energy Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	99.9		99.8
Long-Term Debt, Fair Value	106.3		108.5
Enogex LLC Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	448.4		448.1
Long-Term Debt, Fair Value	493.4		497.9
Enogex LLC Revolving Credit Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	0		150.0
Long-Term Debt, Fair Value	0		150.0
Enogex LLC Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Carrying Amount	250.0		0
Long-Term Debt, Fair Value	250.0		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	0.5		3.8
Energy Derivative Contracts Liabilities	0.3		0.5
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	0.5		3.8
Energy Derivative Contracts Liabilities	0.3		0.5
Long-term Debt [Member] | OG&E [Member] | Due August 31, 2062 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt, gross	$ 10.7		$ 0

[1] In September 2012, OG&E purchased the electric distribution system at Tinker Air Force Base for $10.7 million and began making installment payments over a 50-year term. The fair value of this debt was based on calculating the net present value of the monthly payments discounted by the Company's current borrowing rate. Since the debt was valued using unobservable inputs, it was classified as Level 3 in the fair value hierarchy. This was a non-cash investing and financing activity as discussed in Note 9.