Segments and Related Information (Tables)

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Results from Operations by Reportable Segment

(Millions of Dollars)	2019			2018			2017
Regulated Electric
Operating revenues (a)	$	4,506.6		$	4,508.0		$	4,541.7
Intersegment revenues	0.6			0.8			0.6
Total operating revenue	$	4,507.2		$	4,508.8		$	4,542.3
Depreciation and amortization	742.1			697.8			661.3
Interest charges and financing costs	205.3			199.5			199.8
Income tax expense	36.1			16.4			179.9
Net income	491.0			450.4			462.5
Regulated Natural Gas
Operating revenues (a)	$	571.3		$	583.1		$	531.9
Intersegment revenues	0.8			0.5			0.5
Total operating revenue	$	572.1		$	583.6		$	532.4
Depreciation and amortization	48.8			43.3			38.7
Interest charges and financing costs	15.6			14.8			13.5
Income tax expense	12.4			10.2			10.0
Net income	40.0			34.2			28.4
Other
Operating revenues (a)	$	33.9		$	30.8		$	28.4
Depreciation and amortization	0.4			0.5			0.6
Interest charges and financing costs	—			—			—
Income tax expense	(1.1		)	0.6			9.8
Net income (loss)	11.6			7.7			(0.8		)
Consolidated Total
Total operating revenue (a)	$	5,113.2		$	5,123.2		$	5,103.1
Reconciling eliminations	(1.4		)	(1.3		)	(1.1		)
Consolidated total revenue	$	5,111.8		$	5,121.9		$	5,102.0
Depreciation and amortization	791.3			741.6			700.6
Interest charges and financing costs	220.9			214.3			213.3
Income tax expense	47.4			27.2			199.7
Net income	542.6			492.3			490.1

^(a) 

Operating revenues include $457.4 million, $473.7 million, and $490.2 million of intercompany revenue for the years ended Dec. 31, 2019, 2018 and 2017, respectively. See Note 13 for further information.