REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue receivables (Note 3)	$ 11,526	$ 10,914
Affiliated Entity \| Apache
Accounts, Notes, Loans and Financing Receivable [Line Items]
Due to related parties	$ 10,600

Carrying amount as of the balance sheet date of obligations due all related parties.

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