For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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SUMMARY OF SIGNIFICANT EVENTS AND ACCOUNTING POLICIES - Concentrations of Credit Risk (Details) - Revenue - Concentrations of Credit Risk - customer	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentrations of Credit Risk
Number of customers	2	2	2
Sunoco and Western Refining Inc.
Concentrations of Credit Risk
Percentage of concentration risk	80.00%	77.00%
Sunoco \| Minimum
Concentrations of Credit Risk
Percentage of concentration risk	10.00%	10.00%
Western Refining \| Minimum
Concentrations of Credit Risk
Percentage of concentration risk	10.00%	10.00%
Crestwood and Suncor
Concentrations of Credit Risk
Percentage of concentration risk			58.00%
Crestwood \| Minimum
Concentrations of Credit Risk
Percentage of concentration risk			10.00%
Suncor \| Minimum
Concentrations of Credit Risk
Percentage of concentration risk			10.00%