EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic earnings per share:
Net income		$ 8,590	$ 16,716	$ 14,933	$ 29,079
Weighted-average common shares (in Shares)		29,368,000	30,310,000	29,339,000	30,275,000
Basic earnings per share (in dollars per share)		$ 0.29	$ 0.55	$ 0.51	$ 0.96
Diluted earnings per share:
Net income		$ 8,590	$ 16,716	$ 14,933	$ 29,079
Weighted-average common shares (in Shares)		29,368,000	30,310,000	29,339,000	30,275,000
Effect of dilutive securities:
Employee stock plans (shares)	[1]	666,000	800,000	736,000	875,000
Diluted weighted-average common shares (in Shares)	[1]	30,034,000	31,110,000	30,075,000	31,150,000
Diluted earnings per share (in dollars per share)	[1]	$ 0.29	$ 0.54	$ 0.50	$ 0.93
Stock awards excluded in the computation of diluted earnings per share		0	0	0	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.