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 from external customers	$	2,299,060	$	625,703	$	21,659		$	—		$	2,946,422
Intersegment revenues	297		264		—			(561		)	—
Total revenues	$	2,299,357	$	625,967	$	21,659		$	(561	)	$	2,946,422
Net income (loss)	$	194,153	$	62,927	$	(17,803	)	$	—		$	239,277

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
Three Months Ended March 31, 2016
Operating revenues from external customers	$	2,185,119	$	565,689	$	21,465		$	—		$	2,772,273
Intersegment revenues	335		287		—			(622		)	—
Total revenues	$	2,185,454	$	565,976	$	21,465		$	(622	)	$	2,772,273
Net income (loss)	$	178,237	$	78,338	$	(15,263	)	$	—		$	241,312