Segment Information (Tables)

9 Months Ended

Sep. 30, 2014

Segment Reporting [Abstract]

Results by Reportable Segment

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Three Months Ended Sept. 30, 2014
Operating revenues (a)(b)	$	881,102	$	159,808	$	8,201	$	—		$	1,049,111
Intersegment revenues	95		29		—		(124		)	—
Total revenues	$	881,197	$	159,837	$	8,201	$	(124	)	$	1,049,111
Net income	$	139,751	$	7,235	$	7,173	$	—		$	154,159

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Three Months Ended Sept. 30, 2013
Operating revenues (a)(b)	$	898,811	$	137,349	$	8,140	$	—		$	1,044,300
Intersegment revenues	67		3		—		(70		)	—
Total revenues	$	898,878	$	137,352	$	8,140	$	(70	)	$	1,044,300
Net income	$	158,498	$	3,555	$	4,213	$	—		$	166,266

^(a)    Operating revenues include $2 million of affiliate electric revenue for the three months ended Sept. 30, 2014 and 2013.

^(b)    Operating revenues include $1 million of other affiliate revenue for the three months ended Sept. 30, 2014 and 2013.

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Nine Months Ended Sept. 30, 2014
Operating revenues (a)(b)	$	2,376,935	$	839,332	$	30,091	$	—		$	3,246,358
Intersegment revenues	254		137		—		(391		)	—
Total revenues	$	2,377,189	$	839,469	$	30,091	$	(391	)	$	3,246,358
Net income	$	289,460	$	56,230	$	16,664	$	—		$	362,354

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other		Reconciling Eliminations			Consolidated Total
Nine Months Ended Sept. 30, 2013
Operating revenues (a)(b)	$	2,368,041	$	730,569	$	29,576	$	—		$	3,128,186
Intersegment revenues	215		75		—		(290		)	—
Total revenues	$	2,368,256	$	730,644	$	29,576	$	(290	)	$	3,128,186
Net income	$	322,569	$	46,141	$	11,460	$	—		$	380,170

^(a)    Operating revenues include $8 million and $6 million of affiliate electric revenue for the nine months ended Sept. 30, 2014 and 2013, respectively.

^(b)    Operating revenues include $3 million of other affiliate revenue for the nine months ended Sept. 30, 2014 and 2013.