Segment Information (Tables)

3 Months Ended

Mar. 31, 2018

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
March 31, 2018	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	238,342		$	103,160		$	—		$	—	$	341,502
Cost of sales	57,273			38,804			—			—		96,077
Gross margin	181,069			64,356			—			—		245,425
Operating, general and administrative	54,648			21,219			(1,522		)	—		74,345
Property and other taxes	33,493			9,318			2			—		42,813
Depreciation and depletion	36,153			7,594			8			—		43,755
Operating income	56,775			26,225			1,512			—		84,512
Interest expense	(19,520		)	(1,854		)	(1,596		)	—		(22,970		)
Other income (expense)	490			108			(1,727		)	—		(1,129		)
Income tax (expense) benefit	(498		)	(2,226		)	810			—		(1,914		)
Net income (loss)	$	37,247		$	22,253		$	(1,001	)	$	—	$	58,499
Total assets	$	4,319,798		$	1,065,103		$	15,517		$	—	$	5,400,418
Capital expenditures	$	42,898		$	9,107		$	—		$	—	$	52,005

Three Months Ended
March 31, 2017	Electric			Gas			Other			Eliminations		Total
Operating revenues	$	266,239		$	101,073		$	—		$	—	$	367,312
Cost of sales	85,385			34,432			—			—		119,817
Gross margin	180,854			66,641			—			—		247,495
Operating, general and administrative (1)	56,720			20,900			714			—		78,334
Property and other taxes	31,161			8,764			3			—		39,928
Depreciation and depletion	34,070			7,383			8			—		41,461
Operating income (loss)	58,903			29,594			(725		)	—		87,772
Interest expense	(21,037		)	(1,546		)	(817		)	—		(23,400		)
Other (expense) income (1)	(1,193		)	(501		)	566			—		(1,128		)
Income tax (expense) benefit	(2,887		)	(6,951		)	3,161			—		(6,677		)
Net income	$	33,786		$	20,596		$	2,185		$	—	$	56,567
Total assets	$	4,388,267		$	1,106,062		$	5,972		$	—	$	5,500,301
Capital expenditures	$	41,041		$	10,478		$	—		$	—	$	51,519

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(1)         We adopted ASU 2017-07 on January 1, 2018. As a result, we recorded the non-service cost component of net periodic benefit cost within other expense, net. We adopted this standard retrospectively and $1.9 million and $0.7 million, respectively, were reclassified from electric and gas operating, general and administrative expenses to other expense, net for the three months ended March 31, 2017, to conform to current period presentation.