FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of fair value of long-term debt, including current maturities, and advances for construction

Advances for construction fair values were estimated using broker quotes from companies that frequently purchase these investments.

	December 31, 2017
			Fair Value
	Cost		Level 1		Level 2		Level 3		Total
Long-term debt, including current maturities	$	531,713	$	—	$	607,492	$	—	$	607,492
Advances for construction	182,502		—		75,083		—		75,083
Total	$	714,215	$	—	$	682,575	$	—	$	682,575

	December 31, 2016
			Fair Value
	Cost		Level 1		Level 2		Level 3		Total
Long-term debt, including current maturities	$	557,953	$	—	$	630,510	$	—	$	630,510
Advances for construction	182,448		—		74,460		—		74,460
Total	$	740,401	$	—	$	704,970	$	—	$	704,970