Segment Information (Tables)

3 Months Ended

Mar. 31, 2016

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, 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

(Thousands of Dollars)	Regulated Electric			Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
Three Months Ended March 31, 2015
Operating revenues from external customers	$	2,224,863		$	715,996	$	21,360		$	—		$	2,962,219
Intersegment revenues	330			676		—			(1,006		)	—
Total revenues	$	2,225,193		$	716,672	$	21,360		$	(1,006	)	$	2,962,219
Net income (loss)	$	81,021	(a)	$	83,676	$	(12,631	)	$	—		$	152,066

^(a)  Includes a net of tax charge related to the Monticello LCM/EPU project.  See Note 5.