Report of Business Segments (Tables)

6 Months Ended

Jun. 30, 2017

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 three and six months endedJune 30, 2017 and 2016.

Three Months Ended June 30, 2017	Electric Utility		Natural Gas Midstream Operations			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	586.4	$	—		$	—		$	—		$	586.4
Cost of sales	232.1		—			—			—			232.1
Other operation and maintenance	116.5		0.2			(1.9		)	—			114.8
Depreciation and amortization	73.7		—			1.0			—			74.7
Taxes other than income	20.2		0.3			0.8			—			21.3
Operating income (loss)	143.9		(0.5		)	0.1			—			143.5
Equity in earnings of unconsolidated affiliates	—		29.4			—			—			29.4
Other income	15.6		—			—			—			15.6
Interest expense	35.6		—			1.5			—			37.1
Income tax expense (benefit)	37.7		10.6			(1.7		)	—			46.6
Net income	$	86.2	$	18.3		$	0.3		$	—		$	104.8
Investment in unconsolidated affiliates	$	—	$	1,153.9		$	5.2		$	—		$	1,159.1
Total assets	$	9,199.0	$	1,513.9		$	89.2		$	(381.6	)	$	10,420.5

Three Months Ended June 30, 2016	Electric Utility		Natural Gas Midstream Operations			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	551.4	$	—		$	—		$	—		$	551.4
Cost of sales	197.7		—			—			—			197.7
Other operation and maintenance	124.8		7.8			(5.0		)	—			127.6
Depreciation and amortization	78.4		—			1.7			—			80.1
Taxes other than income	19.1		—			1.0			—			20.1
Operating income (loss)	131.4		(7.8		)	2.3			—			125.9
Equity in earnings of unconsolidated affiliates	—		16.7			—			—			16.7
Other income (expense)	7.0		—			(1.4		)	(0.1		)	5.5
Interest expense	35.0		—			1.1			(0.1		)	36.0
Income tax expense	31.1		9.3			0.2			—			40.6
Net income (loss)	$	72.3	$	(0.4	)	$	(0.4	)	$	—		$	71.5
Investment in unconsolidated affiliates	$	—	$	1,168.8		$	—		$	—		$	1,168.8
Total assets	$	8,380.2	$	1,481.8		$	94.9		$	(297.7	)	$	9,659.2

Six Months Ended June 30, 2017	Electric Utility		Natural Gas Midstream Operations			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	1,042.4	$	—		$	—		$	—		$	1,042.4
Cost of sales	440.8		—			—			—			440.8
Other operation and maintenance	242.6		0.3			(4.1		)	—			238.8
Depreciation and amortization	128.4		—			1.9			—			130.3
Taxes other than income	42.5		0.5			2.2			—			45.2
Operating income (loss)	188.1		(0.8		)	—			—			187.3
Equity in earnings of unconsolidated affiliates	—		65.0			—			—			65.0
Other income (expense)	28.5		0.1			(1.3		)	(0.1		)	27.2
Interest expense	69.2		—			3.0			(0.1		)	72.1
Income tax expense (benefit)	45.0		26.0			(4.4		)	—			66.6
Net income	$	102.4	$	38.3		$	0.1		$	—		$	140.8
Investment in unconsolidated affiliates	$	—	$	1,153.9		$	5.2		$	—		$	1,159.1
Total assets	$	9,199.0	$	1,513.9		$	89.2		$	(381.6	)	$	10,420.5

Six Months Ended June 30, 2016	Electric Utility		Natural Gas Midstream Operations			Other Operations			Eliminations			Total
(In millions)
Operating revenues	$	984.5	$	—		$	—		$	—		$	984.5
Cost of sales	375.6		—			—			—			375.6
Other operation and maintenance	241.1		8.0			(7.6		)	—			241.5
Depreciation and amortization	155.1		—			3.5			—			158.6
Taxes other than income	42.7		—			2.3			—			45.0
Operating income (loss)	170.0		(8.0		)	1.8			—			163.8
Equity in earnings of unconsolidated affiliates	—		45.0			—			—			45.0
Other income (expense)	12.3		—			(1.1		)	(0.2		)	11.0
Interest expense	70.5		—			2.0			(0.2		)	72.3
Income tax expense (benefit)	33.4		19.4			(2.0		)	—			50.8
Net income	$	78.4	$	17.6		$	0.7		$	—		$	96.7
Investment in unconsolidated affiliates	$	—	$	1,168.8		$	—		$	—		$	1,168.8
Total assets	$	8,380.2	$	1,481.8		$	94.9		$	(297.7	)	$	9,659.2