SUBSEQUENT EVENTS - Myrtle Grove Share Purchase and Subscription Agreement (Details) - Subsequent event - USD ($)	Jul. 26, 2019	Jul. 25, 2019
Heartland SPV
Subsequent Event [Line Items]
Percentage acquired	35.00%
Cash and cash equivalents	$ 13,500,000
Vertex Refining LA, LLC | MG SPV
Subsequent Event [Line Items]
Assets acquired		$ 22,666,667
Vertex Refining LA, LLC | MG SPV | Class A
Subsequent Event [Line Items]
Units purchased (in shares)		21,667
Vertex Refining LA, LLC | MG SPV | Class B
Subsequent Event [Line Items]
Units purchased (in shares)		1,000
Vertex Operating | Tensile-MG | Class B
Subsequent Event [Line Items]
Units sold (in shares)		1,000
Units sold, value		$ 1,000,000
MG SPV | Tensile-MG | Class B
Subsequent Event [Line Items]
Units sold (in shares)		3,000
Units sold, value		$ 3,000,000
Maximum transaction costs		$ 850,000
Tensile-MG | MG SPV
Subsequent Event [Line Items]
Percentage acquired		15.58%
Tensile-MG | Heartland SPV
Subsequent Event [Line Items]
Percentage acquired	65.00%
Minimum | MG SPV
Subsequent Event [Line Items]
Indemnification liability		$ 226,000
Maximum | MG SPV
Subsequent Event [Line Items]
Indemnification liability		3,400,000
Maximum | MG SPV | MG SPV
Subsequent Event [Line Items]
Indemnification liability		$ 4,000,000
Subscription Agreement | Tensile-MG
Subsequent Event [Line Items]
Number of shares issued	1,500,000
Number of warrants (in shares)	1,500,000
Warrants value	$ 2,220,000
Warrants, price per share (in dollars per share)	$ 1.48
Exercise price (in dollars per share)	$ 2.25
Warrant term	10 years
Beneficial ownership limitation (as a percent)	4.999%
Beneficial ownership limitation, upon 61 days notice (as a percent)	9.999%
Lock-Up Agreement | Tensile-MG
Subsequent Event [Line Items]
Period of maximum units sold	90 days
Lock-Up Agreement | Maximum | Tensile-MG
Subsequent Event [Line Items]
Number of shares issued	300,000
Warrant term	4 years