FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair Value of Financial Assets and Liabilities
Risk premium percentage	1.70%
Advances for construction	$ 186,342	$ 182,502
Level 1
Fair Value of Financial Assets and Liabilities
Long-term debt, including current maturities, net	0	0
Advances for construction	0	0
Total	0	0
Level 2
Fair Value of Financial Assets and Liabilities
Long-term debt, including current maturities, net	849,551	607,492
Advances for construction	77,204	75,083
Total	926,755	682,575
Level 3
Fair Value of Financial Assets and Liabilities
Long-term debt, including current maturities, net	0	0
Advances for construction	0	0
Total	0	0
Total
Fair Value of Financial Assets and Liabilities
Long-term debt, including current maturities, net	849,551	607,492
Advances for construction	77,204	75,083
Total	926,755	682,575
Cost
Fair Value of Financial Assets and Liabilities
Long-term debt, including current maturities, net	814,938	531,713
Advances for construction	186,342	182,502
Total	$ 1,001,280	$ 714,215

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- Definition

Amount of liability for consideration received or receivable from customer which is not included in transaction price, when consideration is expected to be refunded to customer, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 55
-Paragraph 27
-URI http://asc.fasb.org/extlink&oid=108792157&loc=SL49130611-203046-203046

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Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Fair value of financial and nonfinancial obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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