EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
SHARE-BASED COMPENSATION
Net income	$ 14,277	$ 13,079
Weighted average shares outstanding - basic	29,807,572	30,714,895
Weighted average shares outstanding - diluted	30,041,351	31,001,238
Basic earnings per common share (in dollars per share)	$ 0.48	$ 0.43
Diluted earnings per common share (in dollars per share)	$ 0.48	$ 0.42
Antidilutive securities excluded from the dilutive share calculation (in shares)	0	539
Stock Option
SHARE-BASED COMPENSATION
Dilutive effect of share-based compensation arrangements	233,779	286,343

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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