Segment Information (Tables)

6 Months Ended

Jun. 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
June 30, 2016	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	248,403		$	44,717		$	—		$	—	$	293,120
Cost of sales	72,165			9,528			—			—		81,693
Gross margin	176,238			35,189			—			—		211,427
Operating, general and administrative	51,568			20,585			426			—		72,579
Property and other taxes	27,322			7,883			3			—		35,208
Depreciation and depletion	32,544			7,346			8			—		39,898
Operating income (loss)	64,804			(625		)	(437		)	—		63,742
Interest expense	(24,119		)	(1,814		)	(488		)	—		(26,421		)
Other income	687			271			237			—		1,195
Income tax (expense) benefit	(3,331		)	1,278			(894		)	—		(2,947		)
Net income (loss)	$	38,041		$	(890	)	$	(1,582	)	$	—	$	35,569
Total assets	$	4,221,293		$	1,080,065		$	6,248		—		$	5,307,606
Capital expenditures	$	57,938		$	11,990		$	—		—		$	69,928

Three Months Ended
June 30, 2015	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	221,362		$	49,198		$	—		$	—	$	270,560
Cost of sales	65,918			13,609			—			—		79,527
Gross margin	155,444			35,589			—			—		191,033
Operating, general and administrative	60,838			21,800			(20,918		)	—		61,720
Property and other taxes	25,080			7,371			3			—		32,454
Depreciation and depletion	28,493			7,226			8			—		35,727
Operating income (loss)	41,033			(808		)	20,907			—		61,132
Interest expense	(19,748		)	(2,748		)	(447		)	—		(22,943		)
Other income (expense)	1,659			700			(1,364		)	—		995
Income tax (expense) benefit	(3,558		)	1,217			(5,870		)	—		(8,211		)
Net income (loss)	$	19,386		$	(1,639	)	$	13,226		$	—	$	30,973
Total assets	$	3,994,221		1,057,958			$	7,889		$	—	$	5,060,068
Capital expenditures	$	63,926		10,706			$	—		$	—	$	74,632

Six Months Ended
June 30, 2016	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	489,745		$	135,914		$	—		$	—	$	625,659
Cost of sales	155,789			41,338			—			—		197,127
Gross margin	333,956			94,576			—			—		428,532
Operating, general and administrative	107,011			42,497			2,932			—		152,440
Property and other taxes	54,751			15,872			6			—		70,629
Depreciation and depletion	65,065			14,707			16			—		79,788
Operating income (loss)	107,129			21,500			(2,954		)	—		125,675
Interest expense	(46,174		)	(3,769		)	(987		)	—		(50,930		)
Other income	1,154			580			2,563			—		4,297
Income tax (expense) benefit	(4,346		)	(1,743		)	670			—		(5,419		)
Net income (loss)	$	57,763		$	16,568		$	(708	)	$	—	$	73,623
Total assets	$	4,221,293		$	1,080,065		$	6,248		—		$	5,307,606
Capital expenditures	$	99,563		$	21,683		$	—		—		$	121,246

Six Months Ended
June 30, 2015	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	457,408		$	159,163		$	—		$	—	$	616,571
Cost of sales	129,837			62,081			—			—		191,918
Gross margin	327,571			97,082			—			—		424,653
Operating, general and administrative	120,893			43,711			(21,761		)	—		142,843
Property and other taxes	50,339			14,896			6			—		65,241
Depreciation and depletion	57,047			14,482			17			—		71,546
Operating income	99,292			23,993			21,738			—		145,023
Interest expense	(39,446		)	(5,742		)	(870		)	—		(46,058		)
Other income (expense)	2,941			842			(2,123		)	—		1,660
Income tax expense	(9,811		)	(3,504		)	(4,912		)	—		(18,227		)
Net income	$	52,976		$	15,589		$	13,833		$	—	$	82,398
Total assets	$	3,994,221		1,057,958			$	7,889		$	—	$	5,060,068
Capital expenditures	$	113,987		17,183			$	—		$	—	$	131,170