Report of Business Segments

6 Months Ended

Jun. 30, 2013

Segment Reporting [Abstract]

Report of Business Segments

Report of Business Segments

Previously, the Company's business was divided into three segmentsas follows: (i) electric utility, which is engaged in the generation, transmission, distribution and sale of electric energy, (ii) natural gas transportation and storage and (iii) natural gas gathering and processing. On March 14, 2013,OGE Energy entered into a Master Formation Agreement withthe ArcLight groupand CenterPoint Energy, Inc., pursuant to which OGE Energy, the ArcLight groupand CenterPoint Energy, Inc., agreed to form Enable Midstream Partners to own and operate the midstream businesses of OGE Energy and CenterPointthat will initially be structured as a private limited partnership. As a result, effective May 1, 2013, OGE Energydeconsolidated its interest in Enogex Holdings LLC andbegan accounting for its interest in Enable Midstream Partners using the equity method of accounting. The Company's business is now divided into two segments for financial reporting purposes as follows: (i) electric utility and (ii) natural gas midstream operations. The formernatural gas transportation and storagesegment andnatural gas gathering and processingsegment have been combined into thenatural gas midstream operationssegment and have been restated for all prior periods presented. Equity in earnings of unconsolidated affiliates in the natural gas midstream operations segment includes OGE Energy's equity interest in Enable Midstream Partners from May 1, 2013 through June 30, 2013. Other than equity in earnings of unconsolidated affiliates, all amounts for the natural gas midstream operations segment are through April 30, 2013. Investment in unconsolidated affiliates in the natural gas midstream operations segment includes OGE Energy's investment in Enable Midstream Partners at June 30, 2013. Other Operations primarily includes the operations of the holding company.  Intersegment revenues are recorded at prices comparable to those of unaffiliated customers and are affected by regulatory considerations.  In reviewing its segment operating results, the Company focuses on operating income as its measure of segment profit and loss, and, therefore, has presented this information below.  The following tables summarize the results of the Company's business segments during the threemonths endedJune 30, 2013 and 2012.

Three Months Ended June 30, 2013	Electric Utility		Natural Gas Midstream Operations		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	574.6	$	166.1	$	—		$	(6.5	)	$	734.2
Cost of goods sold	247.6		129.7		—			(6.7		)	370.6
Gross margin on revenues	327.0		36.4		—			0.2			363.6
Other operation and maintenance	107.0		15.7		(0.7		)	—			122.0
Depreciation and amortization	62.0		9.2		3.2			—			74.4
Taxes other than income	19.9		2.5		0.9			—			23.3
Operating income (loss)	$	138.1	$	9.0	$	(3.4	)	$	0.2		$	143.9
Equity in earnings of unconsolidated affiliates	$	—	$	18.5	$	—		$	—		$	18.5
Investment in unconsolidated affiliates	$	—	$	1,267.2	$	—		$	—		$	1,267.2
Total assets	$	7,453.6	$	1,266.8	$	189.4		$	(61.3	)	$	8,848.5

Three Months Ended June 30, 2012	Electric Utility		Natural Gas Midstream Operations		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	528.0	$	344.0	$	—		$	(17.0	)	$	855.0
Cost of goods sold	204.6		222.6		—			(17.9		)	409.3
Gross margin on revenues	323.4		121.4		—			0.9			445.7
Other operation and maintenance	114.7		42.7		(4.4		)	—			153.0
Depreciation and amortization	62.7		24.3		3.5			—			90.5
Impairment of assets	—		0.1		—			—			0.1
Taxes other than income	18.2		5.7		0.9			—			24.8
Operating income (loss)	$	127.8	$	48.6	$	—		$	0.9		$	177.3
Total assets	$	6,833.2	$	2,395.3	$	331.4		$	(208.5	)	$	9,351.4

Six Months Ended June 30, 2013	Electric Utility		Natural Gas Midstream Operations		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	1,030.1	$	630.4	$	—		$	(24.9	)	$	1,635.6
Cost of goods sold	460.6		489.0		—			(26.0		)	923.6
Gross margin on revenues	569.5		141.4		—			1.1			712.0
Other operation and maintenance	212.1		60.9		(3.0		)	—			270.0
Depreciation and amortization	123.3		36.8		6.2			—			166.3
Taxes other than income	43.1		10.5		2.8			—			56.4
Operating income (loss)	$	191.0	$	33.2	$	(6.0	)	$	1.1		$	219.3
Equity in earnings of unconsolidated affiliates	$	—	$	18.5	$	—		$	—		$	18.5
Investment in unconsolidated affiliates	$	—	$	1,267.2	$	—		$	—		$	1,267.2
Total assets	$	7,453.6	$	1,266.8	$	189.4		$	(61.3	)	$	8,848.5

Six Months Ended June 30, 2012	Electric Utility		Natural Gas Midstream Operations			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	954.7	$	773.6		$	—		$	(32.6	)	$	1,695.7
Cost of goods sold	400.1		527.9			—			(33.4		)	894.6
Gross margin on revenues	554.6		245.7			—			0.8			801.1
Other operation and maintenance	225.3		85.0			(9.7		)	—			300.6
Depreciation and amortization	122.4		47.7			7.0			—			177.1
Impairment of assets	—		0.3			—			—			0.3
Gain on insurance proceeds	—		(7.5		)	—			—			(7.5		)
Taxes other than income	39.3		13.0			2.7			—			55.0
Operating income (loss)	$	167.6	$	107.2		$	—		$	0.8		$	275.6
Total assets	$	6,833.2	$	2,395.3		$	331.4		$	(208.5	)	$	9,351.4