Segment and Related Information (Tables)

12 Months Ended

Dec. 31, 2016

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

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

December 31, 2016	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	1,011,595		$	245,652		$	—		$	—	$	1,257,247
Cost of sales	332,817			68,156			—			—		400,973
Gross margin	678,778			177,496			—			—		856,274
Operating, general and administrative	216,736			86,713			(556		)	—		302,893
Property and other taxes	115,583			32,505			10			—		148,098
Depreciation and depletion	130,236			29,067			33			—		159,336
Operating income	216,223			29,211			513			—		245,947
Interest expense, net	(86,038		)	(6,589		)	(2,343		)	—		(94,970		)
Other income, net	3,246			1,329			973			—		5,548
Income tax benefit (expense)	7,392			(1,687		)	1,942			—		7,647
Net income	$	140,823		$	22,264		$	1,085		$	—	$	164,172
Total assets	$	4,363,848		$	1,129,355		$	6,118		$	—	$	5,499,321
Capital expenditures	$	236,014		$	51,887		$	—		$	—	$	287,901

December 31, 2015	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	944,428		$	269,871		$	—		$	—	$	1,214,299
Cost of sales	281,251			91,613			—			—		372,864
Gross margin	663,177			178,258			—			—		841,435
Operating, general and administrative	233,416			84,219			(20,160		)	—		297,475
Property and other taxes	104,264			29,168			10			—		133,442
Depreciation and depletion	115,701			28,968			33			—		144,702
Operating income	209,796			35,903			20,117			—		265,816
Interest expense, net	(79,044		)	(11,433		)	(1,676		)	—		(92,153		)
Other income, net	6,300			1,821			(538		)	—		7,583
Income tax expense	(19,950		)	(3,752		)	(6,335		)	—		(30,037		)
Net income	$	117,102		$	22,539		$	11,568		$	—	$	151,209
Total assets	$	4,185,192		$	1,072,613		$	6,890		$	—	$	5,264,695
Capital expenditures	$	234,451		$	49,254		$	—		$	—	$	283,705

December 31, 2014	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	877,967		$	326,896		$	—		$	—	$	1,204,863
Cost of sales	348,640			133,951			—			—		482,591
Gross margin	529,327			192,945			—			—		722,272
Operating, general and administrative	200,186			91,437			14,263			—		305,886
Property and other taxes	84,759			29,821			12			—		114,592
Depreciation and depletion	94,813			28,930			33			—		123,776
Operating income (loss)	149,569			42,757			(14,308		)	—		178,018
Interest expense, net	(60,424		)	(10,618		)	(6,760		)	—		(77,802		)
Other income, net	4,758			1,324			4,116			—		10,198
Income tax (expense) benefit	(1,490		)	(7,463		)	19,225			—		10,272
Net income	$	92,413		$	26,000		$	2,273		$	—	$	120,686
Total assets	$	3,434,035		$	1,519,196		$	7,671		$	—	$	4,960,902
Capital expenditures	$	233,538		$	36,846		$	—		$	—	$	270,384