EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator for basic and diluted earnings per share:
Net income	$ 60,754	$ 64,418
Numerator for basic and diluted earnings per share	$ 60,754	$ 64,418
Denominator:
Weighted average common shares for basic earnings per share	54,245,133	53,078,529
Net effect of dilutive stock options, restricted stock units and restricted stock awards	2,991,294	3,162,010
Weighted average common shares for diluted earnings per share	57,236,427	56,240,539
Net income per share:
Basic (in dollars per share)	$ 1.12	$ 1.21
Diluted (in dollars per share)	$ 1.06	$ 1.15
Anti-dilutive options not included in the calculation (in shares)	26,203	53,230