NET EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net Earnings (Numerator) [Abstract]
Basic EPS - Net earnings	$ 19,679	$ 16,536	$ 39,025	$ 32,053
Diluted EPS - Net earnings	$ 19,679	$ 16,536	$ 39,025	$ 32,053
Number of Shares (Denominator) [Abstract]
Basic EPS - weighted average common shares outstanding (in shares)	32,077,353	31,798,773	32,031,342	31,752,489
Effect of dilutive securities - stock options, restricted stock, and performance shares (in shares)	360,366	403,782	346,324	442,563
Diluted EPS - weighted average common shares outstanding and effect of stock options, restricted stock, and performance shares (in shares)	32,437,719	32,202,555	32,377,666	32,195,052
Per Share Amount [Abstract]
Basic EPS - Net earnings (in dollars per share)	$ 0.61	$ 0.52	$ 1.22	$ 1.01
Diluted EPS - Net earnings (in dollars per share)	$ 0.61	$ 0.51	$ 1.21	$ 1.00
Stock Options [Member]
Net earnings per share [Abstract]
Anti-dilutive stock options outstanding, excluded from diluted earnings per share calculation (in shares)			190,590	230,108