QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
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Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Quarterly Financial Information Disclosure [Abstract] | |||||||||||
| Operating revenues | $ 57,531 | $ 61,385 | $ 57,878 | $ 54,527 | $ 56,289 | $ 65,006 | $ 63,351 | $ 62,582 | $ 231,321 | $ 247,228 | $ 281,837 |
| Operating income (loss) | (8,359) | (122,773) | (276) | (5,056) | (1,421) | 2,366 | (3,509) | (805) | (136,464) | (3,369) | 24,294 |
| Net income (loss) | 61,459 | (81,215) | (3,072) | (5,787) | (5,648) | (802) | (4,510) | (3,950) | $ (28,615) | $ (14,910) | 7,899 |
| Net income (loss) attributable to common shares | $ 61,694 | $ (81,448) | $ (2,787) | $ (5,620) | $ (5,538) | $ (560) | $ 1,938 | $ (3,818) | $ 8,705 | ||
| Earnings (loss) per common share, basic (in dollars per share) | $ 2.89 | $ (3.91) | $ (0.13) | $ (0.27) | $ (0.27) | $ (0.03) | $ 0.09 | $ (0.19) | $ (1.36) | $ (0.39) | $ 0.42 |
| Earnings (loss) per common share, diluted (in dollars per share) | $ 2.89 | $ (3.91) | $ (0.13) | $ (0.27) | $ (0.27) | $ (0.03) | $ 0.09 | $ (0.19) | $ (1.36) | $ (0.39) | $ 0.42 |
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- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The net result for the period of deducting operating expenses from operating revenues. No definition available.
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- Definition The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- References No definition available.
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- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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