STOCK BASED AND DEFERRED COMPENSATION - Summary of Additional Information Regarding Stock Plan (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | ||
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Mar. 31, 2019 |
Dec. 31, 2018 |
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Summary of stock based compensation agreements | ||||
Unrecognized stock-based compensation cost | $ 28,410 | $ 24,954 | ||
Weighted average years expense recognition period | 2 years 11 months 12 days | 2 years 2 months 27 days | ||
Total stock-based awards outstanding (in shares) | [1] | 1,356,443 | 1,301,745 | |
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