INCOME TAXES - Net Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Investment in partnership	$ 103,195	$ 65,851
Asset retirement obligation	451	220
Net operating losses	26,749	495
Property, plant, and equipment	5,679	0
Other	0	1,212
Total deferred tax assets	136,074	67,778
Valuation allowance	(135,024)	0
Net deferred tax assets	1,050	67,778
Deferred tax liabilities:
Property, plant, and equipment	0	2,863
Other	1,050	0
Net deferred tax assets	$ 0	$ 64,915