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INCENTIVE STOCK PLANS - Summary of Performance Shares (Details) - Performance Shares - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common shares reserved for performance shares granted during year (in shares) 191,203 361,870 232,684
Weighted average fair value of performance share units granted (in dollars per share) $ 36.10 $ 29.59 $ 35.99
Intrinsic value of outstanding performance share units $ 16,360 $ 11,711 $ 10,758
Fair value of performance shares vested 1,738 3,522 6,387
Cash used to purchase common shares from current and former employees to pay withholding tax requirements on restricted shares vested $ 559 $ 992 $ 2,639