Black Hills Power 10-Q 5 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	1-7978
Entity Registrant Name	Black Hills Power, Inc.
Entity Incorporation, State or Country Code	SD
Entity Tax Identification Number	46-0111677
Entity Address, Address Line One	7001 Mount Rushmore Road
Entity Address, City or Town	Rapid City
Entity Address, State or Province	SD
Entity Address, Postal Zip Code	57702
City Area Code	(605)
Local Phone Number	721-1700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		23,416,396
Entity Central Index Key	0000012400
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

Condensed Statements of Compreh

Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 77,022	$ 78,067	$ 225,309	$ 222,558
Operating expenses:
Fuel and purchased power	21,805	25,207	62,919	68,400
Operations and maintenance	20,885	19,851	61,570	57,430
Depreciation and amortization	10,328	9,950	30,762	29,700
Taxes - property	2,000	1,631	6,102	5,741
Total operating expenses	55,018	56,639	161,353	161,271
Operating income	22,004	21,428	63,956	61,287
Other income (expense):
Interest expense incurred (including amortization of debt issuance costs, premiums, and discounts)	(6,101)	(5,632)	(17,807)	(16,873)
Allowance for funds used during construction - borrowed	456	199	1,166	399
Interest income	316	250	603	488
Other income (expense), net	112	(247)	28	(606)
Total other income (expense), net	(5,217)	(5,430)	(16,010)	(16,592)
Income before income taxes	16,787	15,998	47,946	44,695
Income tax expense	(3,044)	(2,681)	(8,558)	(8,493)
Net income	13,743	13,317	39,388	36,202
Other comprehensive income (loss), net of tax:
Reclassification of net realized (gains) losses on settled/amortized interest rate swaps (net of tax of $(3), $(6), $(10) and $(17), respectively)	13	10	38	31
Reclassification adjustment of benefit plan liability - net gain (loss) (net of tax of $(3), $(9), $(10) and $(27), respectively)	12	17	38	51
Other comprehensive income (loss), net of tax	25	27	76	82
Comprehensive income	$ 13,768	$ 13,344	$ 39,464	$ 36,284

Condensed Statements of Compr_2

Condensed Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Reclassification adjustment of cash flow hedges settled, (tax) benefit	$ (3)	$ (6)	$ (10)	$ (17)
Reclassification adjustment of benefit and other postretirement plans included in net income, (tax) benefit	$ (3)	$ (9)	$ (10)	$ (27)

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash	$ 5	$ 112
Accounts receivable, net	24,154	28,431
Accounts receivable from affiliates	6,721	8,119
Materials, supplies and fuel	26,190	24,853
Regulatory assets, current	20,555	19,052
Other current assets	4,296	4,538
Total current assets	81,921	85,105
Investments	4,860	4,889
Property, plant and equipment	1,454,337	1,381,045
Less: accumulated depreciation and amortization	(393,013)	(376,160)
Total property, plant and equipment, net	1,061,324	1,004,885
Other assets:
Regulatory assets, non-current	54,234	56,680
Other assets, non-current	24,006	9,729
Total other assets, non-current	78,240	66,409
TOTAL ASSETS	1,226,345	1,161,288
Current liabilities:
Accounts payable	17,492	25,122
Accounts payable to affiliates	26,648	25,804
Accrued liabilities	45,223	34,193
Money pool notes payable	17,370	38,690
Notes payable to Parent	25,000	0
Regulatory liabilities, current	2,821	2,574
Total current liabilities	134,554	126,383
Long-term debt	340,141	340,035
Deferred credits and other liabilities:
Deferred income tax liabilities, net	116,965	114,009
Regulatory liabilities, non-current	162,821	160,642
Benefit plan liabilities	12,823	14,606
Other deferred credits and other liabilities	15,337	1,368
Total deferred credits and other liabilities	307,946	290,625
Commitments and contingencies (Notes 5, 6 and 9)
Stockholder’s equity:
Common stock $1 par value; 50,000,000 shares authorized; 23,416,396 shares issued	23,416	23,416
Additional paid-in capital	39,575	39,575
Retained earnings	381,528	342,145
Accumulated other comprehensive loss	(815)	(891)
Total stockholder’s equity	443,704	404,245
TOTAL LIABILITIES AND STOCKHOLDER’S EQUITY	$ 1,226,345	$ 1,161,288

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common Stock, Par Value (usd per share)	$ 1	$ 1
Common Stock, Shares authorized	50,000,000	50,000,000
Common Stock, Shares Issued	23,416,396	23,416,396

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net income	$ 39,388	$ 36,202
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	30,762	29,700
Deferred income tax	951	4,619
Employee benefits	584	1,139
Other adjustments, net	2,559	2,123
Change in operating assets and liabilities:
Accounts receivable and other current assets	4,290	224
Accounts payable and other current liabilities	9,370	2,337
Regulatory assets - current	(2,306)	2,004
Regulatory liabilities - current	298	8,224
Payment for Pension Benefits	(1,753)	(1,795)
Other operating activities, net	(667)	(1,400)
Net cash provided by (used in) operating activities	83,476	83,377
Investing activities:
Property, plant and equipment additions	(86,395)	(47,527)
Proceeds from sale of assets	0	4,994
Other investing activities	(868)	(5,338)
Net cash provided by (used in) investing activities	(87,263)	(47,871)
Financing activities:
Change in money pool notes payable, net	(21,320)	(35,509)
Notes payable to Parent	25,000	0
Net cash provided by (used in) financing activities	3,680	(35,509)
Net Cash Provided by (Used in) Continuing Operations [Abstract]
Net change in cash	(107)	(3)
Cash, beginning of period	112	16
Cash, end of period	$ 5	$ 13

Condensed Statements of Common

Condensed Statements of Common Stockholder's Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	AOCI Attributable to Parent
Common Stock, Shares Issued - Beginning Balance at Dec. 31, 2017		23,416,396
Stockholders' Equity - Beginning Balance at Dec. 31, 2017	$ 394,232	$ 23,416	$ 39,575	$ 332,499	$ (1,258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,760			11,760
Other comprehensive income (loss), net of tax	27				27
Dividend to Parent company	(16,000)			(16,000)
Other adjustments	1			1
Common Stock, Shares Issued - Ending Balance at Mar. 31, 2018		23,416,396
Stockholders' Equity - Ending Balance at Mar. 31, 2018	390,020	$ 23,416	39,575	328,260	(1,231)
Common Stock, Shares Issued - Beginning Balance at Dec. 31, 2017		23,416,396
Stockholders' Equity - Beginning Balance at Dec. 31, 2017	394,232	$ 23,416	39,575	332,499	(1,258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,202
Other comprehensive income (loss), net of tax	82
Common Stock, Shares Issued - Ending Balance at Sep. 30, 2018		23,416,396
Stockholders' Equity - Ending Balance at Sep. 30, 2018	394,518	$ 23,416	39,575	332,703	(1,176)
Common Stock, Shares Issued - Beginning Balance at Mar. 31, 2018		23,416,396
Stockholders' Equity - Beginning Balance at Mar. 31, 2018	390,020	$ 23,416	39,575	328,260	(1,231)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,125			11,125
Other comprehensive income (loss), net of tax	28				28
Dividend to Parent company	(10,000)			(10,000)
Common Stock, Shares Issued - Ending Balance at Jun. 30, 2018		23,416,396
Stockholders' Equity - Ending Balance at Jun. 30, 2018	391,173	$ 23,416	39,575	329,385	(1,203)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,317			13,317
Other comprehensive income (loss), net of tax	27				27
Dividend to Parent company	(10,000)			(10,000)
Other adjustments	1			1
Common Stock, Shares Issued - Ending Balance at Sep. 30, 2018		23,416,396
Stockholders' Equity - Ending Balance at Sep. 30, 2018	$ 394,518	$ 23,416	39,575	332,703	(1,176)
Common Stock, Shares Issued - Beginning Balance at Dec. 31, 2018	23,416,396	23,416,396
Stockholders' Equity - Beginning Balance at Dec. 31, 2018	$ 404,245	$ 23,416	39,575	342,145	(891)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,497			15,497
Other comprehensive income (loss), net of tax	12				12
Other adjustments	1			1
Common Stock, Shares Issued - Ending Balance at Mar. 31, 2019		23,416,396
Stockholders' Equity - Ending Balance at Mar. 31, 2019	$ 419,748	$ 23,416	39,575	357,636	(879)
Common Stock, Shares Issued - Beginning Balance at Dec. 31, 2018	23,416,396	23,416,396
Stockholders' Equity - Beginning Balance at Dec. 31, 2018	$ 404,245	$ 23,416	39,575	342,145	(891)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39,388
Other comprehensive income (loss), net of tax	$ 76
Common Stock, Shares Issued - Ending Balance at Sep. 30, 2019	23,416,396	23,416,396
Stockholders' Equity - Ending Balance at Sep. 30, 2019	$ 443,704	$ 23,416	39,575	381,528	(815)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of ASC 842 implementation	(7)			(7)
Common Stock, Shares Issued - Beginning Balance at Mar. 31, 2019		23,416,396
Stockholders' Equity - Beginning Balance at Mar. 31, 2019	419,748	$ 23,416	39,575	357,636	(879)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,148			10,148
Other comprehensive income (loss), net of tax	39				39
Other adjustments	1			1
Common Stock, Shares Issued - Ending Balance at Jun. 30, 2019		23,416,396
Stockholders' Equity - Ending Balance at Jun. 30, 2019	429,936	$ 23,416	39,575	367,785	(840)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,743			13,743
Other comprehensive income (loss), net of tax	$ 25				25
Common Stock, Shares Issued - Ending Balance at Sep. 30, 2019	23,416,396	23,416,396
Stockholders' Equity - Ending Balance at Sep. 30, 2019	$ 443,704	$ 23,416	$ 39,575	$ 381,528	$ (815)

Management's Statement_

Management's Statement:	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Statement	MANAGEMENT’S STATEMENT The unaudited condensed financial statements included herein have been prepared by Black Hills Power, Inc. (the “Company”, “we”, “us”, or “our”), pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to such rules and regulations; however, we believe that the footnotes adequately disclose the information presented. These condensed financial statements should be read in conjunction with the financial statements and the notes thereto, included in our 2018 Annual Report on Form 10-K filed with the SEC. The information furnished in the accompanying condensed financial statements reflects certain estimates required and all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the September 30, 2019 , December 31, 2018 and September 30, 2018 financial information and are of a normal recurring nature. The results of operations for the three and nine months ended September 30, 2019 and September 30, 2018 , and our financial condition as of September 30, 2019 and December 31, 2018 are not necessarily indicative of the results of operations and financial condition to be expected as of or for any other period. Recently Issued Accounting Standards Financial Instruments -- Credit Losses: Measurement of Credit Losses on Financial Instruments, ASU 2018-19 In June 2016, the FASB issued ASU 2016-13, Financial Instruments -- Credit Losses: Measurement of Credit Losses on Financial Instrument s, which was subsequently amended by ASU 2018-19 in November 2018. The standard introduces new accounting guidance for credit losses on financial instruments within its scope, including trade receivables. This new guidance adds an impairment model that is based on expected losses rather than incurred losses. It is effective for interim and annual reporting periods beginning after December 15, 2019, and will be applied on a modified-retrospective basis through a cumulative-effect adjustment to retained earnings as of January 1, 2020. We do not anticipate the adoption of this guidance to have a material impact on our financial position, results of operations or cash flows. Recently Adopted Accounting Standards Leases, ASU 2016-02 In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) to increase transparency and comparability among organizations by requiring the recognition of right-of-use assets and lease liabilities on the balance sheet for most leases, whereas previously only financing-type lease liabilities (capital leases) were recognized on the balance sheet. Under the new standard, disclosures are required to meet the objective of enabling users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. We adopted the standard effective January 1, 2019. We elected the option to not recast comparative periods presented with transitioning to the new lease standard and will report these comparative periods as presented under previous lease guidance. In addition, we elected the package of practical expedients permitted under the transition guidance with the new standard, which among other things, allowed us to carry forward the historical lease classification. We also elected the practical expedient related to land easements, allowing us to carry forward our accounting treatment of existing land easement agreements. Adoption of the new standard resulted in the recording of an operating lease right-of-use asset and an off-setting operating lease obligation liability of $14 million

Revenue_

Revenue:	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue	REVENUE Revenue Recognition As of January 1, 2018, we adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , and its related amendments (collectively known as ASC 606). Revenue is recognized in an amount that reflects the consideration we expect to receive in exchange for goods or services, when control of the promised goods or services is transferred to our customers. The following table depicts the disaggregation of revenue, from contracts with customers by customer type and timing of revenue recognition for the three and nine months ended September 30, 2019 and 2018 . Sales tax and other similar taxes are excluded from revenues. Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in thousands) Customer types: Retail $ 51,056 $ 49,874 $ 150,941 $ 147,040 Wholesale 7,918 8,255 23,041 25,496 Market - off-system sales 5,122 7,625 12,185 13,349 Transmission/Other 12,798 12,183 38,712 36,273 Revenue from contracts with customers 76,894 77,937 224,879 222,158 Other revenues 128 130 430 400 Total revenues $ 77,022 $ 78,067 $ 225,309 $ 222,558 Timing of revenue recognition: Services transferred over time $ 76,894 $ 77,937 $ 224,879 $ 222,158 Revenue from contracts with customers $ 76,894 $ 77,937 $ 224,879 $ 222,158 Contract Balances The nature of our primary revenue contracts provides an unconditional right to consideration upon service delivery; therefore, no customer contract assets or liabilities exist. The unconditional right to consideration is represented by the balance in our Accounts receivable and is further discussed in Note 3. We do not typically incur costs that would be capitalized to obtain or fulfill a revenue contract.

Accounts Receivable_

Accounts Receivable:	9 Months Ended
	Sep. 30, 2019
Accounts Receivable, Net [Abstract]
Accounts Receivable	ACCOUNTS RECEIVABLE Following is a summary of Accounts receivable, net included in the accompanying Condensed Balance Sheets (in thousands) as of: September 30, 2019 December 31, 2018 Accounts receivable, trade $ 14,367 $ 16,236 Unbilled revenues 9,894 12,333 Less allowance for doubtful accounts (107 ) (138 ) Accounts receivable, net $ 24,154 $ 28,431

Regulatory Accounting_

Regulatory Accounting:	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
Regulatory Accounting	REGULATORY ACCOUNTING Our regulated electric operations are subject to regulation by various state and federal agencies. The accounting policies followed are generally subject to the Uniform System of Accounts of the FERC. Our regulatory assets and liabilities were as follows (in thousands) as of: September 30, 2019 December 31, 2018 Regulatory assets: Loss on reacquired debt (a) $ 1,056 $ 1,259 Deferred taxes on AFUDC (b) 4,946 5,020 Employee benefit plans and related deferred taxes (c) 19,935 19,868 Deferred energy and fuel cost adjustments (b) 22,270 20,334 Deferred taxes on flow through accounting (c) 9,392 8,749 Decommissioning costs (a) 6,654 8,196 Vegetation management (a) 8,638 10,366 Other regulatory assets (a) 1,898 1,940 Total regulatory assets $ 74,789 $ 75,732 Less current regulatory assets (20,555 ) (19,052 ) Regulatory assets, non-current $ 54,234 $ 56,680 Regulatory liabilities: Cost of removal for utility plant (a) $ 56,113 $ 52,366 Employee benefit plan costs and related deferred taxes (c) 7,518 7,518 Excess deferred income taxes (c) 98,858 100,276 TCJA revenue reserve 2,821 2,523 Other regulatory liabilities (c) 332 533 Total regulatory liabilities $ 165,642 $ 163,216 Less current regulatory liabilities (2,821 ) (2,574 ) Regulatory liabilities, non-current $ 162,821 $ 160,642 ____________________ (a) We are allowed a recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base. Regulatory Matters There have been no significant changes to our Regulatory Matters from those previously disclosed in Note 1 of the Notes to the Financial Statements in our 2018 Annual Report on Form 10-K except as reported below. Renewable Ready Service Tariffs and Corriedale Wind Energy Project South Dakota Electric and Wyoming Electric received approvals for the Renewable Ready Service Tariffs and related jointly-filed CPCN to construct the $57 million , 40 MW Corriedale Wind Energy Project. The wind project will be jointly owned by the two electric utilities to deliver renewable energy for large commercial, industrial and governmental agency customers. The project is expected to be in service by the end of 2020. In September 2019, the customer subscription period was completed with customer interest fulfilling the 40 MW of available energy. On November 1, 2019, South Dakota Electric filed with the SDPUC an amendment seeking approval to increase the generating capacity under the tariff for the South Dakota portion by 12.5 MW to a total of 32.5 MW.

Related-Party Transactions_

Related-Party Transactions:	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related-Party Transactions	RELATED-PARTY TRANSACTIONS Dividend to Parent We did not record any dividends for the nine months ended September 30, 2019 . We recorded non-cash dividends to our Parent of $36 million and decreased the utility Money pool note receivable by $36 million for the nine months ended September 30, 2018 . Receivables and Payables We have accounts receivable and accounts payable balances related to transactions with other BHC subsidiaries. The balances were as follows (in thousands) as of: September 30, 2019 December 31, 2018 Accounts receivable from affiliates $ 6,721 $ 8,119 Accounts payable to affiliates $ 26,648 $ 25,804 Money Pool Notes Receivable and Notes Payable We participate in the Utility Money Pool Agreement (the Agreement). Under the Agreement, we may borrow from the pool; however the Agreement restricts the pool from loaning funds to BHC or to any of BHC’s non-utility subsidiaries. The Agreement does not restrict us from paying dividends to BHC. Borrowings under the Agreement bear interest at the weighted average daily cost of our parent company’s external borrowings as defined under the Agreement, or if there are no external funds outstanding on that date, then the rate will be the daily one-month LIBOR plus 1.0% . At September 30, 2019 , the average cost of borrowing under the Utility Money Pool was 2.57% . We had the following balances with the Utility Money Pool (in thousands) as of: September 30, 2019 December 31, 2018 Money pool notes payable $ 17,370 $ 38,690 Our net interest income (expense) relating to balances with the Utility Money Pool was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Net interest income (expense) $ (111 ) $ (75 ) $ (582 ) $ (207 ) Notes payable to Parent September 30, 2019 December 31, 2018 Notes payable to Parent (a) $ 25,000 $ — (a) Note bears interest at 4.51% , expires December 31, 2019, and is eligible for annual renewal. Interest payable related to this note was $0.2 million as of September 30, 2019 . Other related party activity was as follows (in thousands): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Revenue: Energy sold to Cheyenne Light $ 326 $ 311 $ 1,240 $ 1,515 Rent from electric properties $ 896 $ 908 $ 2,687 $ 3,025 Horizon Point shared facility revenues $ 3,007 $ 2,826 $ 9,020 $ 8,078 Fuel and purchased power : Purchases of coal from WRDC $ 4,368 $ 4,161 $ 12,241 $ 12,477 Purchase of excess energy from Cheyenne Light $ 239 $ 193 $ 412 $ 361 Purchase of renewable wind energy from Cheyenne Light - Happy Jack $ 316 $ 262 $ 1,193 $ 1,284 Purchase of renewable wind energy from Cheyenne Light - Silver Sage $ 607 $ 582 $ 2,201 $ 2,371 Gas transportation service agreement with Cheyenne Light for firm and interruptible gas transportation $ 76 $ 96 $ 227 $ 288 Operations and maintenance: Corporate support services and fees from Black Hills Service Company $ 9,291 $ 9,836 $ 28,933 $ 25,046 Wygen III ground lease with WRDC $ 247 $ 241 $ 740 $ 722

Employee Benefit Plans_

Employee Benefit Plans:	9 Months Ended
	Sep. 30, 2019
Defined Benefit Plan [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS The components of net periodic benefit cost for the Defined Benefit Pension Plan were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Service cost $ 91 $ 129 $ 274 $ 387 Interest cost 603 548 1,808 1,645 Expected return on plan assets (851 ) (887 ) (2,554 ) (2,660 ) Prior service cost 3 11 8 33 Net loss (gain) 305 516 915 1,548 Net periodic benefit cost $ 151 $ 317 $ 451 $ 953 Defined Benefit Postretirement Healthcare Plan The components of net periodic benefit cost for the Defined Benefit Postretirement Healthcare Plan were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Service cost $ 38 $ 48 $ 112 $ 145 Interest cost 46 45 139 134 Prior service cost (benefit) (84 ) (84 ) (252 ) (252 ) Net periodic benefit cost $ — $ 9 $ (1 ) $ 27 Supplemental Non-qualified Defined Benefit Plans The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit Plans were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Interest cost $ 29 $ 27 $ 86 $ 81 Net loss (gain) 15 26 48 78 Net periodic benefit cost $ 44 $ 53 $ 134 $ 159 Contributions Contributions to the Defined Benefit Pension Plan are cash contributions made directly to the Pension Plan Trust account. Contributions to the Postretirement Healthcare and Supplemental Plans are made in the form of benefit payments. Contributions made for 2019 and anticipated contributions for 2019 and 2020 are as follows (in thousands): Contributions Remaining Anticipated Contributions for Anticipated Contributions for Nine Months Ended September 30, 2019 2019 2020 Defined Benefit Pension Plan $ 1,753 $ — $ 1,720 Defined Benefit Postretirement Healthcare Plan $ 350 $ 117 $ 477 Supplemental Non-qualified Defined Benefit Plans $ 173 $ 58 $ 217

Fair Value of Financial Instrum

Fair Value of Financial Instruments:	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTS Financial instruments for which the carrying amount did not equal the fair value were as follows (in thousands) as of: September 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current maturities (a) (b) $ 340,141 $ 467,040 $ 340,035 $ 412,894 _________________ (a) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy. (b) Carrying amount of long-term debt is net of deferred financing costs.

Supplemental Disclosure of Cash

Supplemental Disclosure of Cash Flow Information:	9 Months Ended
	Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosure of Cash Flow Information	SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION Nine Months Ended September 30, 2019 2018 (in thousands) Non-cash investing and financing activities - Property, plant and equipment acquired with accrued liabilities $ 8,858 $ 10,540 Non-cash (decrease) to money pool notes receivable, net $ — $ (36,000 ) Non-cash dividend to Parent $ — $ 36,000 Cash (paid) refunded during the period for - Interest (net of amounts capitalized) $ (14,946 ) $ (14,104 )

Commitment and Contingencies_

Commitment and Contingencies:	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES There have been no significant changes to commitments and contingencies from those previously disclosed in Note 11 of our Notes to the Financial Statements in our 2018 Annual Report on Form 10-K.

Leases_

Leases:	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	LEASES We have a ground lease for the Wygen III generating facility with an affiliate and communication tower site and operation center facility leases with third parties. Our leases have remaining terms ranging from less than one year to 31 years . The components of lease expense were as follows (in thousands): Income Statement Location Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Operating lease cost Operations and maintenance $ 227 $ 683 Variable lease cost Operations and maintenance 39 121 Total lease cost $ 266 $ 804 Supplemental balance sheet information related to leases was as follows (in thousands): Balance Sheet Location As of September 30, 2019 Assets: Operating lease assets Other assets, non-current $ 14,171 Total lease assets $ 14,171 Liabilities: Current: Operating leases Accrued liabilities $ 198 Noncurrent: Operating leases Other deferred credits and other liabilities 13,993 Total lease liabilities $ 14,191 Supplemental cash flow information related to leases was as follows (in thousands): Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 676 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ — As of September 30, 2019 Weighted average remaining lease term (years): Operating leases 30 years Weighted average discount rate: Operating leases 4.4 % Scheduled maturities of operating lease liabilities for future years were as follows (in thousands): Total 2019 (a) $ 231 2020 856 2021 856 2022 856 2023 853 Thereafter 21,947 Total lease payments $ 25,599 Less imputed interest 11,408 Present value of lease liabilities $ 14,191 (a) Includes lease obligations for the remaining three months of 2019 .

Management's Statement (Policie

Management's Statement (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Leases, ASU 2016-02 In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) to increase transparency and comparability among organizations by requiring the recognition of right-of-use assets and lease liabilities on the balance sheet for most leases, whereas previously only financing-type lease liabilities (capital leases) were recognized on the balance sheet. Under the new standard, disclosures are required to meet the objective of enabling users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. We adopted the standard effective January 1, 2019. We elected the option to not recast comparative periods presented with transitioning to the new lease standard and will report these comparative periods as presented under previous lease guidance. In addition, we elected the package of practical expedients permitted under the transition guidance with the new standard, which among other things, allowed us to carry forward the historical lease classification. We also elected the practical expedient related to land easements, allowing us to carry forward our accounting treatment of existing land easement agreements. Adoption of the new standard resulted in the recording of an operating lease right-of-use asset and an off-setting operating lease obligation liability of $14 million
Revenue Recognition	Revenue Recognition As of January 1, 2018, we adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , and its related amendments (collectively known as ASC 606). Revenue is recognized in an amount that reflects the consideration we expect to receive in exchange for goods or services, when control of the promised goods or services is transferred to our customers. The following table depicts the disaggregation of revenue, from contracts with customers by customer type and timing of revenue recognition for the three and nine months ended September 30, 2019 and 2018 . Sales tax and other similar taxes are excluded from revenues. Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in thousands) Customer types: Retail $ 51,056 $ 49,874 $ 150,941 $ 147,040 Wholesale 7,918 8,255 23,041 25,496 Market - off-system sales 5,122 7,625 12,185 13,349 Transmission/Other 12,798 12,183 38,712 36,273 Revenue from contracts with customers 76,894 77,937 224,879 222,158 Other revenues 128 130 430 400 Total revenues $ 77,022 $ 78,067 $ 225,309 $ 222,558 Timing of revenue recognition: Services transferred over time $ 76,894 $ 77,937 $ 224,879 $ 222,158 Revenue from contracts with customers $ 76,894 $ 77,937 $ 224,879 $ 222,158 Contract Balances The nature of our primary revenue contracts provides an unconditional right to consideration upon service delivery; therefore, no customer contract assets or liabilities exist. The unconditional right to consideration is represented by the balance in our Accounts receivable and is further discussed in Note 3. We do not typically incur costs that would be capitalized to obtain or fulfill a revenue contract.

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 (in thousands) Customer types: Retail $ 51,056 $ 49,874 $ 150,941 $ 147,040 Wholesale 7,918 8,255 23,041 25,496 Market - off-system sales 5,122 7,625 12,185 13,349 Transmission/Other 12,798 12,183 38,712 36,273 Revenue from contracts with customers 76,894 77,937 224,879 222,158 Other revenues 128 130 430 400 Total revenues $ 77,022 $ 78,067 $ 225,309 $ 222,558 Timing of revenue recognition: Services transferred over time $ 76,894 $ 77,937 $ 224,879 $ 222,158 Revenue from contracts with customers $ 76,894 $ 77,937 $ 224,879 $ 222,158

Accounts Receivable (Tables)

Accounts Receivable (Tables)	9 Months Ended
	Sep. 30, 2019
Accounts Receivable, Net [Abstract]
Schedule of Accounts Receivable	Following is a summary of Accounts receivable, net included in the accompanying Condensed Balance Sheets (in thousands) as of: September 30, 2019 December 31, 2018 Accounts receivable, trade $ 14,367 $ 16,236 Unbilled revenues 9,894 12,333 Less allowance for doubtful accounts (107 ) (138 ) Accounts receivable, net $ 24,154 $ 28,431

Regulatory Accounting (Tables)

Regulatory Accounting (Tables)	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
Schedule of Regulatory Assets	Our regulatory assets and liabilities were as follows (in thousands) as of: September 30, 2019 December 31, 2018 Regulatory assets: Loss on reacquired debt (a) $ 1,056 $ 1,259 Deferred taxes on AFUDC (b) 4,946 5,020 Employee benefit plans and related deferred taxes (c) 19,935 19,868 Deferred energy and fuel cost adjustments (b) 22,270 20,334 Deferred taxes on flow through accounting (c) 9,392 8,749 Decommissioning costs (a) 6,654 8,196 Vegetation management (a) 8,638 10,366 Other regulatory assets (a) 1,898 1,940 Total regulatory assets $ 74,789 $ 75,732 Less current regulatory assets (20,555 ) (19,052 ) Regulatory assets, non-current $ 54,234 $ 56,680 Regulatory liabilities: Cost of removal for utility plant (a) $ 56,113 $ 52,366 Employee benefit plan costs and related deferred taxes (c) 7,518 7,518 Excess deferred income taxes (c) 98,858 100,276 TCJA revenue reserve 2,821 2,523 Other regulatory liabilities (c) 332 533 Total regulatory liabilities $ 165,642 $ 163,216 Less current regulatory liabilities (2,821 ) (2,574 ) Regulatory liabilities, non-current $ 162,821 $ 160,642 ____________________ (a) We are allowed a recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base.
Schedule of Regulatory Liabilities	Regulatory liabilities: Cost of removal for utility plant (a) $ 56,113 $ 52,366 Employee benefit plan costs and related deferred taxes (c) 7,518 7,518 Excess deferred income taxes (c) 98,858 100,276 TCJA revenue reserve 2,821 2,523 Other regulatory liabilities (c) 332 533 Total regulatory liabilities $ 165,642 $ 163,216 Less current regulatory liabilities (2,821 ) (2,574 ) Regulatory liabilities, non-current $ 162,821 $ 160,642 ____________________ (a) We are allowed a recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base.

Related-Party Transactions (Tab

Related-Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Schedule of Related Party Accounts Receivable and Payable	The balances were as follows (in thousands) as of: September 30, 2019 December 31, 2018 Accounts receivable from affiliates $ 6,721 $ 8,119 Accounts payable to affiliates $ 26,648 $ 25,804
Schedule of Related Party Notes	We had the following balances with the Utility Money Pool (in thousands) as of: September 30, 2019 December 31, 2018 Money pool notes payable $ 17,370 $ 38,690
Schedule of Related Party Interest Income Expense	Our net interest income (expense) relating to balances with the Utility Money Pool was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Net interest income (expense) $ (111 ) $ (75 ) $ (582 ) $ (207 )
Schedule of Related Party Notes Payable to Parent	Notes payable to Parent September 30, 2019 December 31, 2018 Notes payable to Parent (a) $ 25,000 $ — (a) Note bears interest at 4.51% , expires December 31, 2019, and is eligible for annual renewal. Interest payable related to this note was $0.2 million as of September 30, 2019 .
Schedule of Revenues and Purchases from Related Parties	Other related party activity was as follows (in thousands): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Revenue: Energy sold to Cheyenne Light $ 326 $ 311 $ 1,240 $ 1,515 Rent from electric properties $ 896 $ 908 $ 2,687 $ 3,025 Horizon Point shared facility revenues $ 3,007 $ 2,826 $ 9,020 $ 8,078 Fuel and purchased power : Purchases of coal from WRDC $ 4,368 $ 4,161 $ 12,241 $ 12,477 Purchase of excess energy from Cheyenne Light $ 239 $ 193 $ 412 $ 361 Purchase of renewable wind energy from Cheyenne Light - Happy Jack $ 316 $ 262 $ 1,193 $ 1,284 Purchase of renewable wind energy from Cheyenne Light - Silver Sage $ 607 $ 582 $ 2,201 $ 2,371 Gas transportation service agreement with Cheyenne Light for firm and interruptible gas transportation $ 76 $ 96 $ 227 $ 288 Operations and maintenance: Corporate support services and fees from Black Hills Service Company $ 9,291 $ 9,836 $ 28,933 $ 25,046 Wygen III ground lease with WRDC $ 247 $ 241 $ 740 $ 722

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2019
Defined Benefit Plan [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit cost for the Defined Benefit Pension Plan were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Service cost $ 91 $ 129 $ 274 $ 387 Interest cost 603 548 1,808 1,645 Expected return on plan assets (851 ) (887 ) (2,554 ) (2,660 ) Prior service cost 3 11 8 33 Net loss (gain) 305 516 915 1,548 Net periodic benefit cost $ 151 $ 317 $ 451 $ 953 Defined Benefit Postretirement Healthcare Plan The components of net periodic benefit cost for the Defined Benefit Postretirement Healthcare Plan were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Service cost $ 38 $ 48 $ 112 $ 145 Interest cost 46 45 139 134 Prior service cost (benefit) (84 ) (84 ) (252 ) (252 ) Net periodic benefit cost $ — $ 9 $ (1 ) $ 27 Supplemental Non-qualified Defined Benefit Plans The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit Plans were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Interest cost $ 29 $ 27 $ 86 $ 81 Net loss (gain) 15 26 48 78 Net periodic benefit cost $ 44 $ 53 $ 134 $ 159
Schedule of Defined Benefit Plans Contributions	Contributions made for 2019 and anticipated contributions for 2019 and 2020 are as follows (in thousands): Contributions Remaining Anticipated Contributions for Anticipated Contributions for Nine Months Ended September 30, 2019 2019 2020 Defined Benefit Pension Plan $ 1,753 $ — $ 1,720 Defined Benefit Postretirement Healthcare Plan $ 350 $ 117 $ 477 Supplemental Non-qualified Defined Benefit Plans $ 173 $ 58 $ 217

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Instruments	Financial instruments for which the carrying amount did not equal the fair value were as follows (in thousands) as of: September 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current maturities (a) (b) $ 340,141 $ 467,040 $ 340,035 $ 412,894 _________________ (a) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy. (b) Carrying amount of long-term debt is net of deferred financing costs.

Supplemental Disclosure of Ca_2

Supplemental Disclosure of Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Nine Months Ended September 30, 2019 2018 (in thousands) Non-cash investing and financing activities - Property, plant and equipment acquired with accrued liabilities $ 8,858 $ 10,540 Non-cash (decrease) to money pool notes receivable, net $ — $ (36,000 ) Non-cash dividend to Parent $ — $ 36,000 Cash (paid) refunded during the period for - Interest (net of amounts capitalized) $ (14,946 ) $ (14,104 )

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Lease, Cost	The components of lease expense were as follows (in thousands): Income Statement Location Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 Operating lease cost Operations and maintenance $ 227 $ 683 Variable lease cost Operations and maintenance 39 121 Total lease cost $ 266 $ 804
Lessee Supplemental Balance Sheet Information Related to Leases	Supplemental balance sheet information related to leases was as follows (in thousands): Balance Sheet Location As of September 30, 2019 Assets: Operating lease assets Other assets, non-current $ 14,171 Total lease assets $ 14,171 Liabilities: Current: Operating leases Accrued liabilities $ 198 Noncurrent: Operating leases Other deferred credits and other liabilities 13,993 Total lease liabilities $ 14,191
Lessee Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases was as follows (in thousands): Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 676 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ —
Lessee Supplemental Weighted Average Schedule Related to Leases	As of September 30, 2019 Weighted average remaining lease term (years): Operating leases 30 years Weighted average discount rate: Operating leases 4.4 %
Lessee, Operating Lease, Liability, Maturity	Scheduled maturities of operating lease liabilities for future years were as follows (in thousands): Total 2019 (a) $ 231 2020 856 2021 856 2022 856 2023 853 Thereafter 21,947 Total lease payments $ 25,599 Less imputed interest 11,408 Present value of lease liabilities $ 14,191 (a) Includes lease obligations for the remaining three months of 2019 .

Management Statement (Details)

Management Statement (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operating lease assets	$ 14,171	$ 14,000
Operating Lease, Liability	$ 14,191	$ 14,000

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 76,894	$ 77,937	$ 224,879	$ 222,158
Other revenues	128	130	430	400
Revenues	77,022	78,067	225,309	222,558
Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76,894	77,937	224,879	222,158
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	51,056	49,874	150,941	147,040
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7,918	8,255	23,041	25,496
Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,122	7,625	12,185	13,349
Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 12,798	$ 12,183	$ 38,712	$ 36,273

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts Receivable, Net [Abstract]
Accounts receivable, trade	$ 14,367	$ 16,236
Unbilled revenues	9,894	12,333
Less allowance for doubtful accounts	(107)	(138)
Accounts receivable, net	$ 24,154	$ 28,431

Regulatory Accounting_ Regulato

Regulatory Accounting: Regulatory Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Total regulatory assets	$ 74,789	$ 75,732
Less current regulatory assets	(20,555)	(19,052)
Regulatory assets, non-current	54,234	56,680
Loss on reacquired debt
Regulatory Assets [Line Items]
Total regulatory assets	1,056	1,259
Deferred taxes on AFUDC
Regulatory Assets [Line Items]
Total regulatory assets	4,946	5,020
Employee benefit plan costs and related deferred taxes
Regulatory Assets [Line Items]
Total regulatory assets	19,935	19,868
Deferred energy and fuel cost adjustments
Regulatory Assets [Line Items]
Total regulatory assets	22,270	20,334
Deferred taxes on flow through accounting
Regulatory Assets [Line Items]
Total regulatory assets	9,392	8,749
Decommissioning costs
Regulatory Assets [Line Items]
Total regulatory assets	6,654	8,196
Vegetation management
Regulatory Assets [Line Items]
Total regulatory assets	8,638	10,366
Other regulatory assets
Regulatory Assets [Line Items]
Total regulatory assets	$ 1,898	$ 1,940

Regulatory Accounting_ Regula_2

Regulatory Accounting: Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 165,642	$ 163,216
Less current regulatory liabilities	(2,821)	(2,574)
Regulatory liabilities, non-current	162,821	160,642
Cost of removal for utility plant
Regulatory Liabilities [Line Items]
Total regulatory liabilities	56,113	52,366
Employee benefit plan costs and related deferred taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	7,518	7,518
Excess deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	98,858	100,276
TCJA revenue reserve
Regulatory Liabilities [Line Items]
Total regulatory liabilities	2,821	2,523
Other regulatory liabilities
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 332	$ 533

Regulatory Accounting_ Rate Rev

Regulatory Accounting: Rate Review (Details) - Corriedale Wind Project $ in Millions	Nov. 01, 2019MW	Sep. 30, 2019USD ($)utilityMW
Wyoming Public Service Commission (WPSC) and South Dakota Public Utilities Commission (SDPUC) | South Dakota Electric and Wyoming Electric
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Cost Of Plant Investment | $		$ 57
Utility Plant, Megawatt Capacity		40
Public Utilities, Number of Electric Utilities Jointly Owning Wind Project | utility		2
Customer Subscription Period Was Completed With Customer Interest Fulfilling All Available Energy | Wyoming Public Service Commission (WPSC) and South Dakota Public Utilities Commission (SDPUC) | South Dakota Electric and Wyoming Electric
Public Utilities, General Disclosures [Line Items]
Utility Plant, Megawatt Capacity		40
Amount of Increase sought in Generating Capacity Under Environmental Improvement Adjustment Tariff | South Dakota Public Utilities Commission (SDPUC) | South Dakota Electric | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Utility Plant, Megawatt Capacity	12.5
New Total Sought In Generating Capacity Under Environmental Improvement Adjustment Tariff | South Dakota Public Utilities Commission (SDPUC) | South Dakota Electric | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Utility Plant, Megawatt Capacity	32.5

Related-Party Transactions (Det

Related-Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Non-cash dividend to Parent		$ 10,000	$ 10,000	$ 16,000
Accounts receivable from affiliates	$ 6,721				$ 6,721		$ 8,119
Accounts payable to affiliates	26,648				26,648		25,804
Money pool notes payable	17,370				17,370		38,690
Notes payable to Parent	25,000				25,000		0
Parent
Related Party Transaction [Line Items]
Non-cash dividend to Parent					$ 0	$ 36,000
Commitment fee percentage					1.00%
Related Party, Interest Rate					4.51%
Notes payable to Parent							$ 0
Interest Payable Related Party	200				$ 200
Subsidiary of Common Parent
Related Party Transaction [Line Items]
Non-cash decrease to money pool notes receivable, net					0	36,000
Subsidiary of Common Parent | Energy sold to Cheyenne Light
Related Party Transaction [Line Items]
Revenue	326	311			1,240	1,515
Subsidiary of Common Parent | Rent from electric properties
Related Party Transaction [Line Items]
Revenue	896	908			2,687	3,025
Subsidiary of Common Parent | Horizon Point shared facility revenues
Related Party Transaction [Line Items]
Revenue	3,007	2,826			9,020	8,078
Subsidiary of Common Parent | Purchases of coal from WRDC
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	4,368	4,161			12,241	12,477
Subsidiary of Common Parent | Purchase of excess energy from Cheyenne Light
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	239	193			412	361
Subsidiary of Common Parent | Purchase of renewable wind energy from Cheyenne Light - Happy Jack
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	316	262			1,193	1,284
Subsidiary of Common Parent | Purchase of renewable wind energy from Cheyenne Light - Silver Sage
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	607	582			2,201	2,371
Subsidiary of Common Parent | Gas transportation service agreement with Cheyenne Light for firm and interruptible gas transportation
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	76	96			227	288
Subsidiary of Common Parent | Corporate support services and fees from Black Hills Service Company
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	9,291	9,836			28,933	25,046
Subsidiary of Common Parent | Wygen III ground lease with WRDC
Related Party Transaction [Line Items]
Fuel, purchased power, and operations & maintenance	247	241			$ 740	722
Utility Money Pool
Related Party Transaction [Line Items]
Related Party, Interest Rate					2.57%
Net interest income (expense)	$ (111)	$ (75)			$ (582)	$ (207)

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 91	$ 129	$ 274	$ 387
Interest cost	603	548	1,808	1,645
Expected return on plan assets	(851)	(887)	(2,554)	(2,660)
Prior service cost (benefit)	3	11	8	33
Net loss (gain)	305	516	915	1,548
Net periodic benefit cost	151	317	451	953
Payment for Pension and Other Postretirement Benefits [Abstract]
Contributions			1,753
Remaining Anticipated Contributions for	0		0
Anticipated Contributions for	1,720		1,720
Defined Benefit Postretirement Healthcare Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	38	48	112	145
Interest cost	46	45	139	134
Prior service cost (benefit)	(84)	(84)	(252)	(252)
Net periodic benefit cost	0	9	(1)	27
Payment for Pension and Other Postretirement Benefits [Abstract]
Contributions			350
Remaining Anticipated Contributions for	117		117
Anticipated Contributions for	477		477
Supplemental Non-qualified Defined Benefit Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	29	27	86	81
Net loss (gain)	15	26	48	78
Net periodic benefit cost	44	$ 53	134	$ 159
Payment for Pension and Other Postretirement Benefits [Abstract]
Contributions			173
Remaining Anticipated Contributions for	58		58
Anticipated Contributions for	$ 217		$ 217

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current maturities, carrying amount	$ 340,141	$ 340,035
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current maturities, fair value	$ 467,040	$ 412,894

Supplemental Disclosure of Ca_3

Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Noncash Investing and Financing Items [Abstract]
Property, plant and equipment acquired with accrued liabilities				$ 8,858	$ 10,540
Non-cash dividend to Parent	$ 10,000	$ 10,000	$ 16,000
Interest and Income Taxes Paid Net [Abstract]
Interest (net of amounts capitalized)				(14,946)	(14,104)
Subsidiary of Common Parent
Noncash Investing and Financing Items [Abstract]
Non-cash (decrease) to money pool notes receivable, net				0	(36,000)
Parent
Noncash Investing and Financing Items [Abstract]
Non-cash dividend to Parent				$ 0	$ 36,000

Leases (Details)

Leases (Details)	Sep. 30, 2019
Minimum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	31 years

Leases_ Lease Costs (Details)

Leases: Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 227	$ 683
Variable lease cost	39	121
Total lease cost	$ 266	$ 804

Leases_ Supplemental Balance Sh

Leases: Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Operating lease assets	$ 14,171	$ 14,000
Operating lease liabilities, current	198
Operating lease liabilities, noncurrent	13,993
Total lease liabilities	$ 14,191	$ 14,000

Leases_ Supplemental Cash Flow

Leases: Supplemental Cash Flow Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 676
Right of use assets obtained in exchange for lease obligations	$ 0

Leases_ Weighted Average Inform

Leases: Weighted Average Information (Details)	Sep. 30, 2019
Leases [Abstract]
Weighted average remaining lease term (years)	30 years
Weighted average discount rate	4.40%

Leases_ Future Minimum Payments

Leases: Future Minimum Payments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Leases [Abstract]
2019	$ 231
2020	856
2021	856
2022	856
2023	853
Thereafter	21,947
Total lease payments	25,599
Less imputed interest	11,408
Present value of lease liabilities	$ 14,191	$ 14,000