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RECEIVABLES (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Sep. 29, 2017
Related Party Transaction [Line Items]
Accounts receivable, net	$ 61,187	$ 87,842
Senior Notes Two
Related Party Transaction [Line Items]
Allowance for uncollectible accounts	13,400
Affiliated Entity
Related Party Transaction [Line Items]
Accounts receivable, net	2,300
Affiliated Entity \| High Mesa Agreement
Related Party Transaction [Line Items]
Accounts receivable, net	23,200
Long-term note receivable	9,800	10,100
Allowance for uncollectible accounts	9,800	9,000
NWGP
Related Party Transaction [Line Items]
Due from related parties	1,700	1,700	$ 1,500
Stated interest rate of senior notes			8.00%
HMS \| Senior Notes Two
Related Party Transaction [Line Items]
Long-term note receivable	$ 11,700	$ 11,700
Stated interest rate of senior notes	8.00%