EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 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)	$ 38,996	$ 53,523	$ 154,071	$ 170,517
Income available to common stockholders, diluted (in dollars)	$ 38,996	$ 53,523	$ 154,071	$ 170,517
Shares (Denominator)
Basic (in shares)	62,378	62,592	62,304	62,527
Total average equivalent shares	65,129	64,821	64,822	64,626
Per Share Amount
Net income per share, basic (in dollars per share)	$ 0.63	$ 0.86	$ 2.47	$ 2.73
Net income per share, diluted (in dollars per share)	$ 0.60	$ 0.83	$ 2.38	$ 2.64
Stock options
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	2,659	2,171	2,440	2,046
Restricted stock units
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	92	58	78	53