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INVESTMENT SECURITIES (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 USD ($) Vessel shares | Dec. 31, 2018 USD ($) Vessel | Dec. 31, 2017 USD ($)
Equity Method Investment [Abstract] |  |  |
Number of vessels operated | 23 | 23 |
Carrying value of investment | $ | $ 800 | $ 4,200 |
Consideration for shares disposed | $ | 17,922 | 0 | $ 103,748
Recognized gain (loss) from changes in fair market value | $ | $ (3,200) | $ 0 |
Nordic American Offshore Limited [Member] |  |  |
Equity Method Investment [Abstract] |  |  |
Shares issued (in shares) | shares | 187,815 |  |
Number of shares held (in shares) | shares | 811,538 |  |
Shares held percentage of common stock outstanding | 3.16% |  |
Hermitage Offshore Services Limited [Member] | Platform Supply Vessels [Member] |  |  |
Equity Method Investment [Abstract] |  |  |
Number of vessels operated | 10 |  |
Hermitage Offshore Services Limited [Member] | Anchor Handling Vessels [Member] |  |  |
Equity Method Investment [Abstract] |  |  |
Number of vessels operated | 2 |  |
Hermitage Offshore Services Limited [Member] | Crew Boats [Member] |  |  |
Equity Method Investment [Abstract] |  |  |
Number of vessels operated | 11 |  |

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