Segments and Related Information (Tables)

12 Months Ended

Dec. 31, 2015

Segment Reporting [Abstract]

Results from Operations by Reportable Segment

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
2015
Operating revenues (a)	$	834,998	$	120,147	$	1,396	$	—		$	956,541
Intersegment revenues	419		498		—		(917		)	—
Total revenues	$	835,417	$	120,645	$	1,396	$	(917	)	$	956,541
Depreciation and amortization	$	77,036	$	14,034	$	175	$	—		$	91,245
Interest charges and financing costs	26,494		2,637		90		—			29,221
Income tax expense	40,654		2,501		1,083		—			44,238
Net Income	69,398		4,862		376		—			74,636

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
2014
Operating revenues (a)	$	829,748	$	169,629	$	1,085		$	—		$	1,000,462
Intersegment revenues	497		4,885		—			(5,382		)	—
Total revenues	$	830,245	$	174,514	$	1,085		$	(5,382	)	$	1,000,462
Depreciation and amortization	$	65,978	$	13,501	$	175		$	—		$	79,654
Interest charges and financing costs	23,448		2,358		107			—			25,913
Income tax expense (benefit)	39,621		5,993		(3,211		)	—			42,403
Net Income	59,060		8,714		2,868			—			70,642

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
2013
Operating revenues (a)	$	789,168	$	132,867	$	1,003		$	—		$	923,038
Intersegment revenues	350		1,967		—			(2,317		)	—
Total revenues	$	789,518	$	134,834	$	1,003		$	(2,317	)	$	923,038
Depreciation and amortization	$	64,237	$	12,485	$	175		$	—		$	76,897
Interest charges and financing costs	22,966		2,749		101			—			25,816
Income tax expense	33,691		4,623		(1,905		)	—			36,409
Net Income	51,334		6,501		1,633			—			59,468

^(a)  Operating revenuesinclude $163 million, $145 million and $137 million of intercompany revenue for the years ended Dec. 31, 2015, 2014 and 2013 respectively. See Note 15 for further discussion of related party transactions by operating segment.