STOCK BASED AND DEFERRED COMPENSATION - Summary of Additional Information Regarding Stock Plan (Details) - USD ($) $ in Thousands |
9 Months Ended | 12 Months Ended | ||
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Sep. 30, 2018 |
Dec. 31, 2017 |
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Summary of stock based compensation agreements | ||||
Unrecognized stock-based compensation cost | $ 22,742 | $ 18,439 | ||
Weighted average years expense recognition period | 2 years 5 months 16 days | 2 years 5 months 23 days | ||
Total stock-based awards outstanding (in shares) | [1] | 1,308,289 | 1,269,657 | |
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