Report of Business Segments (Tables)

3 Months Ended

Mar. 31, 2013

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 during the threemonths endedMarch 31, 2013 and 2012.

Three Months Ended March 31, 2013	Electric Utility		Natural Gas Transportation and Storage		Natural Gas Gathering and Processing		Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	455.5	$	216.4	$	317.9	$	—		$	(88.4	)	$	901.4
Cost of goods sold	213.0		182.7		246.4		—			(89.1		)	553.0
Gross margin on revenues	242.5		33.7		71.5		—			0.7			348.4
Other operation and maintenance	105.1		10.9		34.3		(2.3		)	—			148.0
Depreciation and amortization	61.3		5.8		21.8		3.0			—			91.9
Taxes other than income	23.2		4.8		3.2		1.9			—			33.1
Operating income (loss)	$	52.9	$	12.2	$	12.2	$	(2.6	)	$	0.7		$	75.4
Total assets	$	7,138.4	$	2,453.0	$	1,948.9	$	387.2		$	(1,945.7	)	$	9,981.8

Three Months Ended March 31, 2012	Electric Utility		Natural Gas Transportation and Storage		Natural Gas Gathering and Processing			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	426.7	$	169.5	$	304.5		$	—		$	(60.0	)	$	840.7
Cost of goods sold	195.5		131.8		217.9			—			(59.9		)	485.3
Gross margin on revenues	231.2		37.7		86.6			—			(0.1		)	355.4
Other operation and maintenance	110.6		12.1		30.1			(5.3		)	0.1			147.6
Depreciation and amortization	59.7		5.6		17.8			3.5			—			86.6
Impairment of assets	—		—		0.2			—			—			0.2
Gain on insurance proceeds	—		—		(7.5		)	—			—			(7.5		)
Taxes other than income	21.1		4.8		2.5			1.8			—			30.2
Operating income (loss)	$	39.8	$	15.2	$	43.5		$	—		$	(0.2	)	$	98.3
Total assets	$	6,632.8	$	1,950.3	$	1,574.1		$	257.7		$	(1,340.4	)	$	9,074.5