Business Segment Information:

6 Months Ended

Jun. 30, 2020

Segment Reporting Information, Additional Information [Abstract]

Business Segment Information

Business Segment Information

Our reportable segments are based on our method of internal reporting, which is generally segregated by differences in products, services and regulation. All of our operations and assets are located within the United States.

Segment and Corporate and Other information is as follows (in thousands):

Three Months Ended June 30, 2020	External Operating Revenue				Inter-company Operating Revenue				Total Revenues
	Contract Customers		Other Revenues		Contract Customers		Other Revenues
Segment:
Electric Utilities	$	156,197	$	1,627	$	5,376	$	—	$	163,200
Gas Utilities	159,824		512		774		—		161,110
Power Generation	1,242		349		24,476		55		26,122
Mining	6,930		233		7,916		337		15,416
Inter-company eliminations	—		—		(38,542)		(392)		(38,934)
Total	$	324,193	$	2,721	$	—	$	—	$	326,914

Three Months Ended June 30, 2019	External Operating Revenue				Inter-company Operating Revenue				Total Revenues
	Contract Customers		Other Revenues		Contract Customers		Other Revenues
Segment:
Electric Utilities	$	159,140	$	1,977	$	5,237	$	—	$	166,354
Gas Utilities	163,303		1,443		723		—		165,469
Power Generation	1,765		434		13,297		9,212		24,708
Mining	5,538		288		6,890		329		13,045
Inter-company eliminations	—		—		(26,147)		(9,541)		(35,688)
Total	$	329,746	$	4,142	$	—	$	—	$	333,888

Six Months Ended June 30, 2020	External Operating Revenue				Inter-company Operating Revenue				Total Revenues
	Contract Customers		Other Revenues		Contract Customers		Other Revenues
Segment:
Electric Utilities	$	323,700	$	1,850	$	11,789	$	—	$	337,339
Gas Utilities	514,111		6,220		1,552		—		521,883
Power Generation	3,097		792		48,088		111		52,088
Mining	13,494		700		15,755		672		30,621
Inter-company eliminations	—		—		(77,184)		(783)		(77,967)
Total	$	854,402	$	9,562	$	—	$	—	$	863,964

Six Months Ended June 30, 2019	External Operating Revenue				Inter-company Operating Revenue				Total Revenues
	Contract Customers		Other Revenues		Contract Customers		Other Revenues
Segment:
Electric Utilities	$	335,803	$	2,231	$	11,247	$	—	$	349,281
Gas Utilities	574,803		324		1,422		—		576,549
Power Generation	4,022		870		26,509		18,552		49,953
Mining	13,088		557		15,169		660		29,474
Inter-company eliminations	—		—		(54,347)		(19,212)		(73,559)
Total	$	927,716	$	3,982	$	—	$	—	$	931,698

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Adjusted operating income (a):
Electric Utilities	$	33,993	$	33,546	$	69,643	$	74,566
Gas Utilities	18,209		8,557		121,106		111,871
Power Generation	11,402		10,156		22,751		22,123
Mining	3,358		1,640		6,487		5,977
Corporate and Other	(29)		102		131		(405)
Operating income	66,933		54,001		220,118		214,132
Interest expense, net	(35,545)		(34,264)		(70,998)		(68,981)
Impairment of investment	—		—		(6,859)		—
Other income (expense), net	(1,863)		263		490		(526)
Income tax (expense)	(4,831)		(2,307)		(20,833)		(19,570)
Net income	24,694		17,693		121,918		125,055
Net income attributable to noncontrolling interest	(3,728)		(3,110)		(7,778)		(6,664)
Net income available for common stock	$	20,966	$	14,583	$	114,140	$	118,391

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(a) Adjusted operating income recognizes intersegment revenues and costs for Colorado Electric’s PPA with Black Hills Colorado IPP on an accrual basis rather than as a finance lease. This presentation of segment information does not impact consolidated financial results.

Segment and Corporate and Other balances included in the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands):

Total assets (net of inter-company eliminations) as of:	June 30, 2020		December 31, 2019
Segment:
Electric Utilities	$	2,982,841	$	2,900,983
Gas Utilities	4,052,860		4,032,339
Power Generation	407,107		417,715
Mining	79,774		77,175
Corporate and Other	167,350		130,245
Total assets	$	7,689,932	$	7,558,457