Summary of Significant Accounting Policies Property, Plant and Equipment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 11,891.9		$ 10,814.9
Accumulated Depreciation	3,547.1		3,340.9
Property, Plant and Equipment, Net	8,344.8		7,474.0
Cost to Return Plant to Service	29.6
Proceeds from insurance	7.6		7.4		0
Gain on insurance proceeds	(7.5)		(3.0)		0
Capitalized Computer Software, Gross	33.1		25.1
Capitalized Computer Software, Amortization	14.1		9.2		10.1
McClain Plant [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	77.00%
Property, Plant and Equipment, Gross	182.1
Accumulated Depreciation	56.3
Property, Plant and Equipment, Net	125.8
Redbud Plant [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	51.00%
Property, Plant and Equipment, Gross	458.5	[1]
Accumulated Depreciation	69.5	[1]
Property, Plant and Equipment, Net	389.0	[1]
Amount of Acquisition Adjustments	148.3
Amount of Acquistion Adjustments Related Accumulated Amortization	23.3
OGE Energy [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	142.1		124.6
Accumulated Depreciation	103.2		90.6
Property, Plant and Equipment, Net	38.9		34.0
Capitalized Computer Software, Gross	11.6		14.0
Capitalized Computer Software, Amortization	6.8		6.4		5.3
OG&E [Member]
Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Gross	17.6		6.7
Capitalized Computer Software, Amortization	4.2		1.8		2.6
Enogex [Member]
Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Gross	3.9		4.4
Capitalized Computer Software, Amortization	3.1		1.0		2.2
Total Property Plant and Equipment [Member] | OGE Energy [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	142.1		124.6
Accumulated Depreciation	103.2		90.6
Property, Plant and Equipment, Net	38.9		34.0
Total Property Plant and Equipment [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	8,749.7		8,143.2
Accumulated Depreciation	2,705.6		2,592.3
Property, Plant and Equipment, Net	6,044.1		5,550.9
Total Property Plant and Equipment [Member] | Enogex [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,000.1		2,547.1
Accumulated Depreciation	738.3		658.0
Property, Plant and Equipment, Net	2,261.8		1,889.1
Electric Transmission and Distribution [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,222.7		2,981.3
Accumulated Depreciation	969.6		920.3
Property, Plant and Equipment, Net	2,253.1		2,061.0
Electric Generation Equipment [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,446.6	[2]	3,360.6	[3]
Accumulated Depreciation	1,242.4	[2]	1,215.8	[3]
Property, Plant and Equipment, Net	2,204.2	[2]	2,144.8	[3]
Amount of Acquistion Adjustments Related Accumulated Amortization			17.9
Transmission Equipment [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Amount of Acquisition Adjustments	3.3		3.3
Amount of Acquistion Adjustments Related Accumulated Amortization	0.3		0.2
Electric Transmission [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,712.6	[4]	1,464.2	[5]
Accumulated Depreciation	359.8	[4]	339.6	[5]
Property, Plant and Equipment, Net	1,352.8	[4]	1,124.6	[5]
Finite-Lived Intangible Assets, Major Class Name [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	50.2		43.2
Accumulated Depreciation	25.0		20.3
Property, Plant and Equipment, Net	25.2		22.9
Property, Plant and Equipment, Other Types [Member] | OG&E [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	317.6		293.9
Accumulated Depreciation	108.8		96.3
Property, Plant and Equipment, Net	208.8		197.6
Transportation and Storage [Member] | Enogex [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	988.6		967.0
Accumulated Depreciation	292.7		277.0
Property, Plant and Equipment, Net	695.9		690.0
Gas Gathering and Processing Equipment [Member] | Enogex [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,011.5		1,580.1
Accumulated Depreciation	445.6		381.0
Property, Plant and Equipment, Net	1,565.9		1,199.1
Gathering and Processing [Member]
Property, Plant and Equipment [Line Items]
Gain on insurance proceeds	$ (7.5)		$ (3.0)

[1] This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $23.3 million.

[2] This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $23.3 million.

[3] This amount includes a plant acquisition adjustment of $148.3 million and accumulated amortization of $17.9 million.

[4] This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.3 million.

[5] This amount includes a plant acquisition adjustment of $3.3 million and accumulated amortization of $0.2 million.