EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Earning per share
Authorized common stock (in shares)	199,000		199,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Income (Numerator)
Income available to common stockholders, basic (in dollars)	$ 63,004	$ 59,300
Income available to common stockholders, diluted (in dollars)	$ 63,004	$ 59,300
Shares (Denominator)
Basic (in shares)	62,964	62,128
Total average equivalent shares	65,349	64,414
Per Share Amount
Net income per share, basic (in dollars per share)	$ 1.00	$ 0.95
Net income per share, diluted (in dollars per share)	$ 0.96	$ 0.92
Stock options
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	2,222	2,216
Restricted stock units
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	163	70