NET EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Net Earnings (Numerator) [Abstract]
Basic EPS - Net earnings	$ 19,346	$ 15,518
Diluted EPS - Net earnings	$ 19,346	$ 15,518
Number of Shares (Denominator) [Abstract]
Basic EPS - weighted average common shares outstanding (in shares)	31,985,332	31,706,205
Effect of dilutive securities - stock options, restricted stock, and performance shares (in shares)	342,001	483,415
Diluted EPS - weighted average common shares outstanding and effect of stock options, restricted stock, and performance shares (in shares)	32,327,333	32,189,620
Per Share Amount [Abstract]
Basic EPS - Net earnings (in dollars per share)	$ 0.60	$ 0.49
Diluted EPS - Net earnings (in dollars per share)	$ 0.60	$ 0.48
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive stock options outstanding, excluded from diluted earnings per share calculation (in shares)	347,211	217,860

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 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.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

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