Segment Information (Tables)

6 Months Ended

Jun. 30, 2018

Segment Reporting [Abstract]

Results from Operations by Reportable Segment

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas			All Other			Reconciling Eliminations			Consolidated Total
Three Months Ended June 30, 2018
Operating revenues (a)	$	209,502	$	21,981		$	271		$	—		$	231,754
Intersegment revenues	106		127			—			(233		)	—
Total revenues	$	209,608	$	22,108		$	271		$	(233	)	$	231,754
Net income (loss)	$	15,481	$	(148	)	$	(144	)	$	—		$	15,189

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas			All Other		Reconciling Eliminations			Consolidated Total
Three Months Ended June 30, 2017
Operating revenues (a)	$	210,742	$	19,027		$	257	$	—		$	230,026
Intersegment revenues	123		68			—		(191		)	—
Total revenues	$	210,865	$	19,095		$	257	$	(191	)	$	230,026
Net income (loss)	$	14,516	$	(973	)	$	698	$	—		$	14,241

^(a)  Operating revenues include $38 million and $43 million of affiliate electric revenue for the three months ended June 30, 2018 and 2017, respectively.

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Six Months Ended June 30, 2018
Operating revenues (a)	$	425,868	$	78,481	$	549	$	—		$	504,898
Intersegment revenues	215		275		—		(490		)	—
Total revenues	$	426,083	$	78,756	$	549	$	(490	)	$	504,898
Net income	$	35,925	$	10,250	$	430	$	—		$	46,605

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Six Months Ended June 30, 2017
Operating revenues (a)	$	427,051	$	67,374	$	532	$	—		$	494,957
Intersegment revenues	219		182		—		(401		)	—
Total revenues	$	427,270	$	67,556	$	532	$	(401	)	$	494,957
Net income	$	29,986	$	5,572	$	1,102	$	—		$	36,660

^(a)  Operating revenues include $76 million and $85 million of affiliate electric revenue for the six months ended June 30, 2018 and 2017, respectively.