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SHAREHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Dec. 12, 2017 | Sep. 30, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2013 | Jun. 16, 2017 | Dec. 31, 2007
Authorized Shares [Roll forward] |  |  |  |  |  |  |  |
Balance at beginning of period (in shares) |  |  | 180,000,000 |  |  |  |  |
Balance at end of period (in shares) |  |  | 180,000,000 | 180,000,000 |  |  |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |  |  |
Balance at beginning of period, issued (in shares) |  |  | 101,969,666 |  |  |  |  |
Balance at beginning of period, outstanding (in shares) |  |  | 101,969,666 |  |  |  |  |
Common Shares Issued in Follow-on Offering (in shares) |  |  | 0 |  |  |  |  |
Balance at end of period, issued (in shares) |  |  | 141,969,666 | 101,969,666 |  |  |  |
Balance at end of period, outstanding (in shares) |  |  | 141,969,666 | 101,969,666 |  |  |  |
Common Stock [Roll forward] |  |  |  |  |  |  |  |
Equity incentive plan issuance |  |  |  | $ 1 |  |  |  |
Common Shares Issued in Follow-on Offering, value |  |  | $ 103,748 | 120,069 |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |
Net proceeds from underwritten public offering of common shares |  | $ 120,100 | 103,748 | 120,068 | $ 0 |  |  |
Additional Paid in Capital [Abstract] |  |  |  |  |  |  |  |
Share premium fund |  |  | 103,400 | 215,500 |  |  |  |
Reduction of share premium | $ 215,500 |  |  |  |  |  |  |
Contributed Surplus Account [Abstract] |  |  |  |  |  |  |  |
Dividend paid |  |  | 59,100 | 125,700 |  |  |  |
Contribution to surplus account |  |  | $ 796,800 | $ 640,500 |  |  |  |
Shareholders' Rights Plan [Abstract] |  |  |  |  |  |  |  |
Preferred share purchase right |  |  | one preferred stock purchase right to purchase one one-thousandth of a share of our Series A Participating Preferred Stock for each outstanding share of its common stock, par value $0.01 per share |  |  |  |  |
Common Share, par value (in dollars per share) |  |  | $ 0.01 | $ 0.01 |  |  | $ 0.01 | $ 0.01
Shareholders rights, exercise price (in dollars per share) |  |  |  |  |  |  | $ 30 | $ 115
Percentage of common share ownership |  |  |  |  |  |  | 15.00% | 15.00%
Shares issued under dividend reinvestment plan (in shares) |  |  |  |  |  | 1,664,450 |  |
Common Stock [Member] |  |  |  |  |  |  |  |
Authorized Shares [Roll forward] |  |  |  |  |  |  |  |
Balance at beginning of period (in shares) |  |  | 180,000,000 | 180,000,000 | 180,000,000 |  |  |
Balance at end of period (in shares) |  |  | 180,000,000 | 180,000,000 | 180,000,000 |  |  |
Issued and Outstanding Shares [Roll forward] |  |  |  |  |  |  |  |
Balance at beginning of period, issued (in shares) |  |  | 101,969,666 | 89,182,001 | 89,182,001 |  |  |
Balance at beginning of period, outstanding (in shares) |  |  | 101,969,666 | 89,182,001 | 89,182,001 |  |  |
Equity incentive plan issuance (in shares) |  |  |  | 137,665 |  |  |  |
Common Shares Issued in Follow-on Offering (in shares) |  |  | 40,000,000 | 12,650,000 |  |  |  |
Balance at end of period, issued (in shares) |  |  | 141,969,666 | 101,969,666 | 89,182,001 |  |  |
Balance at end of period, outstanding (in shares) |  |  | 141,969,666 | 101,969,666 | 89,182,001 |  |  |
Common Stock [Roll forward] |  |  |  |  |  |  |  |
Balance at beginning of period |  |  | $ 1,020 | $ 892 | $ 892 |  |  |
Equity incentive plan issuance |  |  |  | 1 |  |  |  |
Common Shares Issued in Follow-on Offering, value |  |  | 400 | 127 |  |  |  |
Balance at end of period |  |  | $ 1,420 | $ 1,020 | $ 892 |  |  |

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