Report of Business Segments (Tables)

12 Months Ended

Dec. 31, 2012

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment [Table Text Block]

The following tables summarize the results of the Company's business segments for the years endedDecember 31, 2012, 2011and2010.

2012	Electric Utility		Natural Gas Transportation and Storage		Natural Gas Gathering and Processing			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	2,141.2	$	639.5	$	1,222.6		$	—		$	(332.1	)	$	3,671.2
Cost of goods sold	879.1		504.9		868.7			—			(334.0		)	1,918.7
Gross margin on revenues	1,262.1		134.6		353.9			—			1.9			1,752.5
Other operation and maintenance	446.3		49.8		123.1			(17.7		)	—			601.5
Depreciation and amortization	248.7		24.0		84.8			13.5			—			371.0
Impairment of assets	—		—		0.4			—			—			0.4
Gain on insurance proceeds	—		—		(7.5		)	—			—			(7.5		)
Taxes other than income	77.7		15.7		12.6			4.2			—			110.2
Operating income (loss)	$	489.4	$	45.1	$	140.5		$	—		$	1.9		$	676.9
Total assets	$	7,222.4	$	2,330.8	$	1,868.6		$	272.6		$	(1,772.2	)	$	9,922.2
Capital expenditures (A)	$	704.4	$	32.0	$	475.4		$	18.3		$	(0.9	)	$	1,229.2

(A) Includes$78.6 millionrelated to the acquisition of certain gas gathering assetsas discussed in Note 3.

2011	Electric Utility		Natural Gas Transportation and Storage		Natural Gas Gathering and Processing			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	2,211.5	$	880.1	$	1,167.1		$	—		$	(342.8	)	$	3,915.9
Cost of goods sold	1,013.5		736.0		870.7			—			(342.3		)	2,277.9
Gross margin on revenues	1,198.0		144.1		296.4			—			(0.5		)	1,638.0
Other operation and maintenance	436.0		50.7		111.8			(17.3		)	—			581.2
Depreciation and amortization	216.1		22.0		55.6			13.4			—			307.1
Impairment of assets	—		—		6.3			—			—			6.3
Gain on insurance proceeds	—		—		(3.0		)	—			—			(3.0		)
Taxes other than income	73.6		15.0		7.0			4.1			—			99.7
Operating income (loss)	$	472.3	$	56.4	$	118.7		$	(0.2	)	$	(0.5	)	$	646.7
Total assets	$	6,620.9	$	1,836.9	$	1,483.8		$	166.6		$	(1,202.2	)	$	8,906.0
Capital expenditures (A)	$	844.5	$	41.1	$	572.0		$	13.8		$	(0.6	)	$	1,470.8

(A) Includes$200.4 millionrelated to the acquisition of certain gas gathering assetsas discussed in Note 3.

2010	Electric Utility		Natural Gas Transportation and Storage		Natural Gas Gathering and Processing		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	2,109.9	$	984.8	$	1,005.6	$	—		$	(383.4	)	$	3,716.9
Cost of goods sold	1,000.2		834.5		733.3		—			(380.6		)	2,187.4
Gross margin on revenues	1,109.7		150.3		272.3		—			(2.8		)	1,529.5
Other operation and maintenance	418.1		53.8		91.5		(13.6		)	—			549.8
Depreciation and amortization	208.7		21.2		50.1		11.3			—			291.3
Impairment of assets	—		0.7		0.4		—			—			1.1
Taxes other than income	69.2		14.2		6.4		3.6			—			93.4
Operating income (loss)	$	413.7	$	60.4	$	123.9	$	(1.3	)	$	(2.8	)	$	593.9
Total assets	$	5,898.1	$	1,316.6	$	973.8	$	135.4		$	(654.8	)	$	7,669.1
Capital expenditures	$	631.6	$	72.6	$	164.0	$	14.1		$	(2.4	)	$	879.9