Segment Information (Tables)

6 Months Ended

Jun. 30, 2013

Segment Reporting [Abstract]

Results from Continuing Operations by Reportable Segment

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Three Months Ended June 30, 2013
Operating revenues	$	747,882	$	209,296	$	9,251	$	—		$	966,429
Intersegment revenues	61		25		—		(86		)	—
Total revenues	$	747,943	$	209,321	$	9,251	$	(86	)	$	966,429
Net income	$	85,603	$	8,786	$	2,910	$	—		$	97,299

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Three Months Ended June 30, 2012
Operating revenues	$	714,651	$	147,398	$	7,452	$	—		$	869,501
Intersegment revenues	43		19		—		(62		)	—
Total revenues	$	714,694	$	147,417	$	7,452	$	(62	)	$	869,501
Net income	$	88,807	$	5,529	$	1,071	$	—		$	95,407

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Six Months Ended June 30, 2013
Operating revenues	$	1,469,230	$	593,220	$	21,436	$	—		$	2,083,886
Intersegment revenues	149		72		—		(221		)	—
Total revenues	$	1,469,379	$	593,292	$	21,436	$	(221	)	$	2,083,886
Net income	$	164,071	$	42,585	$	7,248	$	—		$	213,904

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Six Months Ended June 30, 2012
Operating revenues	$	1,396,930	$	530,402	$	18,221	$	—		$	1,945,553
Intersegment revenues	135		74		—		(209		)	—
Total revenues	$	1,397,065	$	530,476	$	18,221	$	(209	)	$	1,945,553
Net income	$	150,140	$	33,839	$	4,713	$	—		$	188,692