SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Capital expenditures accrued	$ 42,160	$ 37,984
Direct operating expense accrued	22,119	7,541
Sourced water purchases accrued	9,531	4,670
Other	2,815	1,609
Total accrued liabilities	$ 76,625	$ 51,804	[1]

[1] See Note 1 for information regarding the basis of financial statement presentation.