Report of Business Segments

9 Months Ended

Sep. 30, 2013

Segment Reporting [Abstract]

Report of Business Segments

Report of Business Segments

Prior to May 1, 2013, the Company's business was divided into three segments as 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 with the ArcLight group and CenterPoint Energy, Inc., pursuant to which OGE Energy, the ArcLight Group and CenterPoint Energy, Inc., agreed to form Enable Midstream Partners to own and operate the midstream businesses of OGE Energy and CenterPoint that 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 September 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 represents OGE Energy's investment in Enable Midstream Partners at September 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 three and ninemonths endedSeptember 30, 2013 and 2012.

Three Months Ended September 30, 2013	Electric Utility		Natural Gas Midstream Operations		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	723.2	$	—	$	—		$	—		$	723.2
Cost of goods sold	273.0		—		—			—			273.0
Gross margin on revenues	450.2		—		—			—			450.2
Other operation and maintenance	105.9		—		(3.7		)	—			102.2
Depreciation and amortization	62.5		—		2.9			—			65.4
Taxes other than income	20.8		—		0.9			—			21.7
Operating income (loss)	$	261.0	$	—	$	(0.1	)	$	—		$	260.9
Equity in earnings of unconsolidated affiliates	$	—	$	46.0	$	—		$	—		$	46.0
Investment in unconsolidated affiliates (at historical cost)	$	—	$	1,295.8	$	—		$	—		$	1,295.8
Total assets	$	7,704.0	$	1,311.3	$	172.2		$	(43.3	)	$	9,144.2

Three Months Ended September 30, 2012	Electric Utility		Natural Gas Midstream Operations		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	721.0	$	412.4	$	—		$	(20.0	)	$	1,113.4
Cost of goods sold	271.8		288.6		—			(20.8		)	539.6
Gross margin on revenues	449.2		123.8		—			0.8			573.8
Other operation and maintenance	108.6		42.3		(3.8		)	—			147.1
Depreciation and amortization	63.5		26.5		3.0			—			93.0
Taxes other than income	19.1		9.8		0.8			—			29.7
Operating income (loss)	$	258.0	$	45.2	$	—		$	0.8		$	304.0
Total assets	$	7,082.3	$	2,562.7	$	276.6		$	(215.6	)	$	9,706.0

Nine Months Ended September 30, 2013	Electric Utility		Natural Gas Midstream Operations		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	1,753.3	$	630.4	$	—		$	(24.9	)	$	2,358.8
Cost of goods sold	733.6		489.0		—			(26.0		)	1,196.6
Gross margin on revenues	1,019.7		141.4		—			1.1			1,162.2
Other operation and maintenance	318.0		60.9		(6.7		)	—			372.2
Depreciation and amortization	185.8		36.8		9.1			—			231.7
Taxes other than income	63.9		10.5		3.7			—			78.1
Operating income (loss)	$	452.0	$	33.2	$	(6.1	)	$	1.1		$	480.2
Equity in earnings of unconsolidated affiliates	$	—	$	64.5	$	—		$	—		$	64.5
Investment in unconsolidated affiliates (at historical cost)	$	—	$	1,295.8	$	—		$	—		$	1,295.8
Total assets	$	7,704.0	$	1,311.3	$	172.2		$	(43.3	)	$	9,144.2

Nine Months Ended September 30, 2012	Electric Utility		Natural Gas Midstream Operations			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	1,675.7	$	1,186.0		$	—		$	(52.6	)	$	2,809.1
Cost of goods sold	671.9		816.5			—			(54.2		)	1,434.2
Gross margin on revenues	1,003.8		369.5			—			1.6			1,374.9
Other operation and maintenance	333.9		127.3			(13.5		)	—			447.7
Depreciation and amortization	185.9		74.2			10.0			—			270.1
Impairment of assets	—		0.3			—			—			0.3
Gain on insurance proceeds	—		(7.5		)	—			—			(7.5		)
Taxes other than income	58.4		22.8			3.5			—			84.7
Operating income (loss)	$	425.6	$	152.4		$	—		$	1.6		$	579.6
Total assets	$	7,082.3	$	2,562.7		$	276.6		$	(215.6	)	$	9,706.0