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
-Topic 275
-SubTopic 10
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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
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Data Type:	num:percentItemType
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Significant Accounting Policies (Major Customers) (Details Textuals 1)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Marathon Petroleum Company
Product Information [Line Items]
Revenue from major customer (percentage)		10.00%	14.00%
Plains Marketing LP
Product Information [Line Items]
Revenue from major customer (percentage)	24.00%	22.00%	20.00%
HuntCrudeOilSupplyCompany [Member]
Product Information [Line Items]
Revenue from major customer (percentage)	10.00%