SHARE PURCHASE AND SUBSCRIPTION AGREEMENTS - Heartland Share Purchase and Subscription Agreement (Details) $ / shares in Units, $ in Millions		6 Months Ended
	Jan. 17, 2020 USD ($) member $ / shares shares	Jun. 30, 2021	Jun. 30, 2020
Common Class A
Class of Stock
Capital investment, percentage (as a percent)	50.00%
Heartland SPV
Class of Stock
Ownership percentage (as a percent)		35.00%
Number of managers | member	5
Conversion basis ratio (in shares)	1
Annual return (as a percent)		22.50%
Vertex Refining OH, LLC
Class of Stock
Ownership percentage (as a percent)	100.00%
Tensile-Heartland | Preferred Class A
Class of Stock
Preferred stock, dividend percentage (as a percent)	22.50%
Tensile-Heartland | Heartland SPV
Class of Stock
Ownership percentage (as a percent)	65.00%		65.00%
Number of managers | member	3
Tensile-Heartland | Heartland SPV | Preferred Class A
Class of Stock
Ownership percentage (as a percent)	100.00%
Vertex Operating | Heartland SPV
Class of Stock
Ownership percentage (as a percent)	35.00%
Number of managers | member	2
Heartland SPV | Common Class A
Class of Stock
Redemption period	180 days
Redemption price, percentage (as a percent)	25.00%
Heartland SPV | Tensile-Heartland | Class A-2 Preferred Units
Class of Stock
Share price (in usd per share) | $ / shares	$ 1,000
Additional consideration (in shares)	7,000
Heartland SPV | Heartland SPV
Class of Stock
Percentage acquired (as a percent)	50.00%
Vertex Refining OH, LLC | Heartland SPV | Common Class A
Class of Stock
Consideration transferred (in shares)	13,500
Vertex Refining OH, LLC | Heartland SPV | A-1 Preferred Units
Class of Stock
Consideration transferred (in shares)	13,500
Vertex Refining OH, LLC | Heartland SPV | Common Class B
Class of Stock
Consideration transferred (in shares)	11,300
Vertex Splitter Corporation | Vertex Refining OH, LLC | Heartland SPV | Common Class B
Class of Stock
Consideration transferred (in shares)	248
Vertex Operating | MG SPV | Common Class A
Class of Stock
Consideration transferred (in shares)	1,000
Share price (in usd per share) | $ / shares	$ 1,000
Equity interest issued or issuable | $	$ 1.0
Vertex Operating | Heartland SPV | Tensile-Heartland | Common Class A
Class of Stock
Consideration transferred (in shares)	13,500
Total purchase price | $	$ 13.5
Vertex Operating | Heartland SPV | Tensile-Heartland | A-1 Preferred Units
Class of Stock
Consideration transferred (in shares)	13,500
Heartland SPV | Heartland SPV | Tensile-Heartland | Common Class A
Class of Stock
Consideration transferred (in shares)	7,500
Total purchase price | $	$ 7.5
Heartland SPV | Heartland SPV | Tensile-Heartland | A-1 Preferred Units
Class of Stock
Consideration transferred (in shares)	7,500
Tensile-MG | MG SPV | MG SPV
Class of Stock
Percentage acquired (as a percent)		15.58%
MG SPV | Tensile-MG
Class of Stock
Ownership interest (as a percent)	15.00%
MG SPV | Vertex Operating
Class of Stock
Ownership interest (as a percent)	85.00%