Segment Information (Tables)

6 Months Ended

Jun. 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 June 30, 2014
Operating revenues from external customers	$	2,297,638	$	369,127	$	18,331		$	—		$	2,685,096
Intersegment revenues	437		1,118		—			(1,555		)	—
Total revenues	$	2,298,075	$	370,245	$	18,331		$	(1,555	)	$	2,685,096
Net income (loss)	$	185,677	$	15,297	$	(5,810	)	$	—		$	195,164

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
Three Months Ended June 30, 2013
Operating revenues from external customers	$	2,219,877	$	341,321	$	17,715		$	—		$	2,578,913
Intersegment revenues	308		557		—			(865		)	—
Total revenues	$	2,220,185	$	341,878	$	17,715		$	(865	)	$	2,578,913
Net income (loss)	$	201,084	$	15,960	$	(20,187	)	$	—		$	196,857

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
Six Months Ended June 30, 2014
Operating revenues from external customers	$	4,599,348	$	1,248,815	$	39,537		$	—		$	5,887,700
Intersegment revenues	790		4,370		—			(5,160		)	—
Total revenues	$	4,600,138	$	1,253,185	$	39,537		$	(5,160	)	$	5,887,700
Net income (loss)	$	371,110	$	92,633	$	(7,358	)	$	—		$	456,385

(Thousands of Dollars)	Regulated Electric		Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
Six Months Ended June 30, 2013
Operating revenues from external customers	$	4,312,073	$	1,010,917	$	38,772		$	—		$	5,361,762
Intersegment revenues	609		1,057		—			(1,666		)	—
Total revenues	$	4,312,682	$	1,011,974	$	38,772		$	(1,666	)	$	5,361,762
Net income (loss)	$	375,190	$	80,870	$	(22,633	)	$	—		$	433,427