Segment Information (Tables)

3 Months Ended

Mar. 31, 2017

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 March 31, 2017
Operating revenues (a)(b)	$	711,388	$	356,136	$	13,010	$	—		$	1,080,534
Intersegment revenues	92		56		—		(148		)	—
Total revenues	$	711,480	$	356,192	$	13,010	$	(148	)	$	1,080,534
Net income	$	76,144	$	34,483	$	919	$	—		$	111,546

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Three Months Ended March 31, 2016
Operating revenues (a)(b)	$	717,462	$	328,494	$	11,885	$	—		$	1,057,841
Intersegment revenues	81		45		—		(126		)	—
Total revenues	$	717,543	$	328,539	$	11,885	$	(126	)	$	1,057,841
Net income	$	72,536	$	40,890	$	2,448	$	—		$	115,874

^(a)    Operating revenues include $2 million of affiliate electric revenue for the three months ended March 31, 2017 and 2016.

^(b)    Operating revenues include $1 million of other affiliate revenue for the three months ended March 31, 2017 and 2016.