Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Interest Rate Swap [Abstract]
Term of debt on utilities rated A- used to discount prospective cash flows	30 years
Reduction in fair value of swap liability	$ 35
Fair Value Measurements [Abstract]
Customers' advances for construction	7,214	$ 6,849
Note receivable	255	255
Fair Value on a Recurring Basis [Member]
Interest Rate Swap [Abstract]
Interest rate swap	2,010	1,815
Fair Value on a Recurring Basis [Member] \| Fair Value Measurements at Reporting Date Using Significant Other Observable Inputs (Level 2) [Member]
Interest Rate Swap [Abstract]
Interest rate swap	2,010	1,815
Carrying Amount [Member]
Fair Value, Financial Liabilities [Abstract]
Total long-term debt	96,798	95,908
Estimated Fair Value [Member]
Fair Value, Financial Liabilities [Abstract]
Total long-term debt	$ 110,000	$ 105,000

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as noncurrent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
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-Section 45
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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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An amount representing an agreement for an unconditional promise by the maker to pay the Entity (holder) a definite sum of money at a future date more than one year from the balance sheet date, net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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The increase or decrease in the value of an interest rate swap due to a contractual agreement tied to the company's credit rating.

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Term of debt on utilities rated A- used in discounting prospective cash flows anticipated to be made under the swap agreement reflecting a representation of the yield to maturity.

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