Segments and Related Information (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Results from Operations by Reportable Segment

(Millions of Dollars)	2018			2017			2016
Regulated Electric
Operating revenues (a)	$	878.6		$	881.9		$	849.9
Intersegment revenues	0.4			0.5			0.4
Total operating revenue	$	879.0		$	882.4		$	850.3
Depreciation and amortization	97.8			88.9			81.3
Interest charges and financing costs	31.8			29.4			29.7
Income tax expense	28.4			38.9			40.5
Net income	85.5			70.9			65.0
Regulated Natural Gas
Operating revenues (a)	$	141.6		$	122.4		$	106.2
Intersegment revenues	0.4			0.3			0.5
Total operating revenue	$	142.0		$	122.7		$	106.7
Depreciation and amortization	28.1			22.1			16.8
Interest charges and financing costs	3.3			2.8			2.9
Income tax expense	4.5			4.0			2.4
Net income	12.5			7.8			4.5
All Other
Operating revenues (a)	$	1.3		$	1.2		$	1.1
Depreciation and amortization	0.2			0.2			0.2
Interest charges and financing costs	0.1			—			—
Income tax (benefit)	(0.6		)	1.3			—
Net (loss)	—			0.7			(0.4		)
Consolidated Total
Total operating revenue	$	1,022.3		$	1,006.3		$	958.1
Reconciling eliminations	(0.8		)	(0.8		)	(0.9		)
Consolidated total revenue	$	1,021.5		$	1,005.5		$	957.2
Depreciation and amortization	126.1			111.2			98.3
Interest charges and financing costs	35.2			32.2			32.6
Income tax expense	32.3			44.2			42.9
Net income	98.0			79.4			69.1

^(a)  Operating revenues include $157.9 million, $177.2 million and $170.5 million of intercompany revenue for the years ended Dec. 31, 2018, 2017 and 2016, respectively. See Note 13 for further information.