EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
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)	$ 59,300	$ 51,820
Income available to common stockholders, diluted (in dollars)	$ 59,300	$ 51,820
Shares (Denominator)
Basic (in shares)	62,128	62,355
Total average equivalent shares	64,414	64,234
Per Share Amount
Net income per share, basic (in dollars per share)	$ 0.95	$ 0.83
Net income per share, diluted (in dollars per share)	$ 0.92	$ 0.81
Stock options
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	2,216	1,827
Restricted stock units
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	70	52