SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Other Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Advances for construction	$ 186,342	$ 182,502
Maximum collection period in which deferred net WRAM and MCBA revenues and associated costs will be recognized	24 months
Minimum collection period after net receivable balances were recognized in which the Company defers net WRAM and MCBA operating revenues and associated costs	12 months
Asset retirement obligation	$ 24,300	$ 21,200