EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Earning per share
Authorized common stock (in shares)	199,000		199,000		199,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Income (Numerator)
Income available to common stockholders, basic (in dollars)	$ 55,775	$ 65,174	$ 115,075	$ 116,994
Income available to common stockholders, diluted (in dollars)	$ 55,775	$ 65,174	$ 115,075	$ 116,994
Shares (Denominator)
Basic (in shares)	62,402	62,631	62,266	62,494
Total average equivalent shares	64,850	64,828	64,640	64,519
Per Share Amount
Net income per share, basic (in dollars per share)	$ 0.89	$ 1.04	$ 1.85	$ 1.87
Net income per share, diluted (in dollars per share)	$ 0.86	$ 1.01	$ 1.78	$ 1.81
Stock options
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	2,358	2,144	2,293	1,973
Restricted stock units
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	90	53	81	52