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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration Risk (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 USD ($) customer item | Dec. 31, 2017 USD ($) customer item | Dec. 31, 2016 customer
Concentration Risk |  |  |
Number of financial institutions with which the entity maintains its cash and cash equivalents | item | 4 | 4 |
Cash insured by financial institutions | $ | $ 0 | $ 0 |
Voyage Revenues | Customer Concentration Risk |  |  |
Concentration Risk |  |  |
Number of customers | 182 | 102 | 52
Major Customers | 0 | 2 | 3
Concentration risk percentage (as a percent) | 10.00% | 10.00% | 10.00%
Voyage Revenues | Customer Concentration Risk | Swissmarine Services S.A. |  |  |
Concentration Risk |  |  |
Concentration risk percentage (as a percent) |  | 15.09% | 25.31%
Voyage Revenues | Customer Concentration Risk | Clipper Group |  |  |
Concentration Risk |  |  |
Concentration risk percentage (as a percent) |  | 10.98% | 22.96%
Voyage Revenues | Customer Concentration Risk | Pioneer Navigation Ltd |  |  |
Concentration Risk |  |  |
Concentration risk percentage (as a percent) |  |  | 11.11%

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- Definition Represents the number of financial institutions with which the entity maintains its cash and cash equivalents. + References No definition available. + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611 + Details
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