Segment Information (Tables)

9 Months Ended

Sep. 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 Sept. 30, 2018
Operating revenues (a)	$	240,344	$	15,355		$	298	$	—		$	255,997
Intersegment revenues	112		(33		)	—		(79		)	—
Total revenues	$	240,456	$	15,322		$	298	$	(79	)	$	255,997
Net income (loss)	$	34,256	$	(3,448	)	$	200	$	—		$	31,008

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas			All Other			Reconciling Eliminations			Consolidated Total
Three Months Ended Sept. 30, 2017
Operating revenues (a)	$	232,802	$	14,394		$	315		$	—		$	247,511
Intersegment revenues	144		56			—			(200		)	—
Total revenues	$	232,946	$	14,450		$	315		$	(200	)	$	247,511
Net income (loss)	$	24,594	$	(2,184	)	$	(85	)	$	—		$	22,325

^(a)  Operating revenues include $40 million and $46 million of affiliate electric revenue for the three months ended Sept. 30, 2018 and 2017, respectively.

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Nine Months Ended Sept. 30, 2018
Operating revenues (a)	$	666,212	$	93,836	$	847	$	—		$	760,895
Intersegment revenues	327		242		—		(569		)	—
Total revenues	$	666,539	$	94,078	$	847	$	(569	)	$	760,895
Net income	$	70,181	$	6,802	$	630	$	—		$	77,613

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Nine Months Ended Sept. 30, 2017
Operating revenues (a)	$	659,853	$	81,768	$	847	$	—		$	742,468
Intersegment revenues	363		238		—		(601		)	—
Total revenues	$	660,216	$	82,006	$	847	$	(601	)	$	742,468
Net income	$	54,580	$	3,388	$	1,017	$	—		$	58,985

^(a)  Operating revenues include $116 million and $131 million of affiliate electric revenue for the nine months ended Sept. 30, 2018 and 2017, respectively.