NET EARNINGS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings (Numerator) [Abstract]
Basic EPS - Net earnings									$ 55,972	$ 59,722	$ 52,826
Diluted EPS - Net earnings									$ 55,972	$ 59,722	$ 52,826
Number of Shares (Denominator) [Abstract]
Basic EPS - weighted average common shares outstanding (in shares)									31,521,667	31,158,142	30,381,310
Effect of dilutive securities - stock options, restricted stock, and performance shares (in shares)									400,971	477,496	790,412
Diluted EPS - weighted average common shares outstanding and effect of stock options and restricted stock (in shares)									31,922,638	31,635,638	31,171,722
Per Share Amount [Abstract]
Basic EPS - Net earnings (in dollars per share)	$ 0.51	$ 0.44	$ 0.45	$ 0.38	$ 0.50	$ 0.45	$ 0.48	$ 0.49	$ 1.78	$ 1.92	$ 1.74
Diluted EPS - Net earnings (in dollars per share)	$ 0.50	$ 0.44	$ 0.44	$ 0.37	$ 0.49	$ 0.44	$ 0.47	$ 0.48	$ 1.75	$ 1.89	$ 1.69
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)									2,500	194,372	56,500