SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of credit risk (Details 5) - Accounts Receivable - Credit Concentration Risk	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	46.00%	0.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	19.00%	43.00%

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
-Publisher FASB
-Name Accounting Standards Codification
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