Segment and Related Information

12 Months Ended

Dec. 31, 2012

Segment Reporting [Abstract]

Segment and Related Information

   Segment and Related Information

Our reportable business segments are primarily engaged in the electric and natural gas business. The remainder of our operations are presented as other, which is not considered a business unit. Other primarily consists of a remaining unregulated natural gas capacity contract, the wind down of our captive insurance subsidiary and our unallocated corporate costs.

We evaluate the performance of these segments based on gross margin. The accounting policies of the operating segments are the same as the parent except that the parent allocates some of its operating expenses to the operating segments according to a methodology designed by management for internal reporting purposes and involves estimates and assumptions. Financial data for the business segments are as follows (in thousands):

December 31, 2012	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	805,554		263,394			$	1,394		$	—	$	1,070,342
Cost of sales	277,826			117,608			—			—		395,434
Gross margin	527,728			145,786			1,394			—		674,908
Operating, general and administrative	187,599			75,971			6,396			—		269,966
MSTI impairment	24,039			—			—			—		24,039
Property and other taxes	72,755			24,907			12			—		97,674
Depreciation	86,559			19,452			33			—		106,044
Operating income (loss)	156,776			25,456			(5,047		)	—		177,185
Interest expense	(55,118		)	(9,063		)	(881		)	—		(65,062		)
Other income	2,630			1,633			109			—		4,372
Income tax (expense) benefit	(22,298		)	(692		)	4,901			—		(18,089		)
Net income (loss)	$	81,990		$	17,334		$	(918	)	$	—	$	98,406
Total assets	$	2,442,602		$	1,032,259		$	10,672		$	—	$	3,485,533
Capital expenditures	$	178,325		$	40,909		$	—		$	—	$	219,234

December 31, 2011	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	797,562		$	318,335		$	1,419		$	—	$	1,117,316
Cost of sales	327,126			167,433			—			—		494,559
Gross margin	470,436			150,902			1,419			—		622,757
Operating, general and administrative	183,503			80,431			3,226			—		267,160
Property and other taxes	66,425			22,686			11			—		89,122
Depreciation	81,859			19,034			33			—		100,926
Operating income (loss)	138,649			28,751			(1,851		)	—		165,549
Interest expense	(54,394		)	(10,432		)	(2,033		)	—		(66,859		)
Other income	2,563			1,258			110			—		3,931
Income tax (expense) benefit	(14,049		)	(3,472		)	7,456			—		(10,065		)
Net income	$	72,769		$	16,105		$	3,682		$	—	$	92,556
Total assets	$	2,259,189		$	938,876		$	12,373		$	—	$	3,210,438
Capital expenditures	$	146,576		$	42,154		$	—		$	—	$	188,730

December 31, 2010	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	790,701		$	318,735		$	1,284		$	—	$	1,110,720
Cost of sales	356,325			174,764			—			—		531,089
Gross margin	434,376			143,971			1,284			—		579,631
Operating, general and administrative	169,483			71,088			(3,524		)	—		237,047
Property and other taxes	65,027			23,159			12			—		88,198
Depreciation	74,227			17,509			33			—		91,769
Operating income	125,639			32,215			4,763			—		162,617
Interest expense	(49,576		)	(12,608		)	(3,642		)	—		(65,826		)
Other income	5,954			284			107			—		6,345
Income tax expense	(18,939		)	(4,183		)	(2,638		)	—		(25,760		)
Net income (loss)	$	63,078		$	15,708		$	(1,410	)	$	—	$	77,376
Total assets	$	2,136,784		$	887,799		$	13,086		$	—	$	3,037,669
Capital expenditures	$	187,212		$	41,161		$	—		$	—	$	228,373