Segment Information (Tables)

9 Months Ended

Sep. 30, 2016

Segment Reporting Information [Line Items]

Schedule of Segment Reporting Information, by Segment [Table Text Block]

Financial data for the business segments are as follows (in thousands):

Three Months Ended
September 30, 2016	Electric			Gas			Other			Eliminations		Total
Operating revenues	266,629			$	34,369		$	—		$	—	$	300,998
Cost of sales	89,681			6,475			—			—		96,156
Gross margin	176,948			27,894			—			—		204,842
Operating, general and administrative	50,460			19,141			(1,311		)	—		68,290
Property and other taxes	32,343			8,328			2			—		40,673
Depreciation and depletion	32,549			7,206			8			—		39,763
Operating income (loss)	61,596			(6,781		)	1,301			—		56,116
Interest expense	(19,099		)	(1,249		)	(701		)	—		(21,049		)
Other income (loss)	982			345			(1,448		)	—		(121		)
Income tax benefit	7,946			1,169			544			—		9,659
Net income (loss)	$	51,425		$	(6,516	)	$	(304	)	$	—	$	44,605
Total assets	$	4,294,549		$	1,093,333		$	6,059		—		$	5,393,941
Capital expenditures	$	66,322		$	16,430		$	—		—		$	82,752

Three Months Ended
September 30, 2015	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	238,513		$	34,226		$	—		$	—	$	272,739
Cost of sales	66,197			7,380			—			—		73,577
Gross margin	172,316			26,846			—			—		199,162
Operating, general and administrative	58,298			19,843			1,155			—		79,296
Property and other taxes	28,648			7,062			2			—		35,712
Depreciation and depletion	28,476			7,209			8			—		35,693
Operating income (loss)	56,894			(7,268		)	(1,165		)	—		48,461
Interest expense	(19,078		)	(2,562		)	(403		)	—		(22,043		)
Other income	1,832			507			1,430			—		3,769
Income tax (expense) benefit	(6,553		)	1,883			(1,719		)	—		(6,389		)
Net income (loss)	$	33,095		$	(7,440	)	$	(1,857	)	$	—	$	23,798
Total assets	$	4,169,423		$	1,057,919		$	7,736		$	—	$	5,235,078
Capital expenditures	$	57,813		$	14,341		$	—		$	—	$	72,154

Nine Months Ended
September 30, 2016	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	756,374		$	170,283		$	—		$	—	$	926,657
Cost of sales	245,470			47,813			—			—		293,283
Gross margin	510,904			122,470			—			—		633,374
Operating, general and administrative	157,471			61,638			1,621			—		220,730
Property and other taxes	87,094			24,200			8			—		111,302
Depreciation and depletion	97,614			21,913			24			—		119,551
Operating income (loss)	168,725			14,719			(1,653		)	—		181,791
Interest expense	(65,273		)	(5,018		)	(1,688		)	—		(71,979		)
Other income	2,136			925			1,115			—		4,176
Income tax benefit (expense)	3,600			(574		)	1,214			—		4,240
Net income (loss)	$	109,188		$	10,052		$	(1,012	)	$	—	$	118,228
Total assets	$	4,294,549		$	1,093,333		$	6,059		—		$	5,393,941
Capital expenditures	$	165,885		$	38,113		$	—		—		$	203,998

Nine Months Ended
September 30, 2015	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	695,921		$	193,389		$	—		$	—	$	889,310
Cost of sales	196,034			69,461			—			—		265,495
Gross margin	499,887			123,928			—			—		623,815
Operating, general and administrative	179,191			63,554			(20,606		)	—		222,139
Property and other taxes	78,987			21,958			8			—		100,953
Depreciation and depletion	85,523			21,691			25			—		107,239
Operating income	156,186			16,725			20,573			—		193,484
Interest expense	(58,524		)	(8,304		)	(1,273		)	—		(68,101		)
Other income (expense)	4,773			1,349			(693		)	—		5,429
Income tax expense	(16,364		)	(1,621		)	(6,631		)	—		(24,616		)
Net income	$	86,071		$	8,149		$	11,976		$	—	$	106,196
Total assets	$	4,169,423		1,057,919			$	7,736		$	—	$	5,235,078
Capital expenditures	$	171,800		31,524			$	—		$	—	$	203,324