Segment Information (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2018
Operating revenues (a)(b)	$	698,274	$	363,986	$	11,038	$	—		$	1,073,298
Intersegment revenues	112		64		—		(176		)	—
Total revenues	$	698,386	$	364,050	$	11,038	$	(176	)	$	1,073,298
Net income	$	79,551	$	53,712	$	459	$	—		$	133,722

(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 (loss)	$	76,144	$	34,483	$	919	$	—		$	111,546

^(a)    Operating revenues include $1 million and $2 million of affiliate electric revenue for the three months ended March 31, 2018 and 2017.

^(b)    Operating revenues include $1 million of other affiliate revenue for the three months ended March 31, 2018 and 2017.