EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Basic earnings per share:
NET INCOME		$ 11,513	$ 16,111	$ 26,446	$ 45,190
Weighted-average common shares		28,855,000	30,013,000	29,175,000	30,186,000
Basic earnings per share		$ 0.40	$ 0.54	$ 0.91	$ 1.50
Diluted earnings per share:
NET INCOME		$ 11,513	$ 16,111	$ 26,446	$ 45,190
Weighted-average common shares		28,855,000	30,013,000	29,175,000	30,186,000
Effect of dilutive awards:
Employee stock plans		443,000	744,000	681,000	867,000
Diluted weighted-average common shares		29,298,000	30,757,000	29,856,000	31,053,000
Diluted earnings per share	[1]	$ 0.39	$ 0.52	$ 0.89	$ 1.46
Stock awards excluded in the computation of diluted earnings per share		69,000	0	8,000	0

[1] The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has excluded the shares underlying the 2015 and 2014 awards in the 2015 and 2014 calculations, respectively, as those shares were not contingently issuable as of the end of the period.