EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Basic earnings per share:
Net income (loss)	$ 14,354	$ 16,111	$ 16,716	$ 12,363	$ 16,037	$ 16,654	$ 13,672	$ 10,903	$ 59,544		$ 57,266		$ (34,404)
Weighted-average common shares	29,350,000	30,013,000	30,310,000	30,239,000	29,974,000	29,762,000	29,178,000	28,754,000	29,976,000		29,421,000		28,636,000
Basic earnings (loss) per share	$ 0.49	$ 0.54	$ 0.55	$ 0.41	$ 0.54	$ 0.56	$ 0.47	$ 0.38	$ 1.99		$ 1.95		$ (1.20)
Diluted earnings per share:
Net income (loss)	$ 14,354	$ 16,111	$ 16,716	$ 12,363	$ 16,037	$ 16,654	$ 13,672	$ 10,903	$ 59,544		$ 57,266		$ (34,404)
Weighted-average common shares	29,350,000	30,013,000	30,310,000	30,239,000	29,974,000	29,762,000	29,178,000	28,754,000	29,976,000		29,421,000		28,636,000
Effect of dilutive securities:
Employee stock plans									853,000	[1]	999,000	[1]	0	[1]
Diluted weighted average common shares	30,051,000	30,757,000	31,110,000	31,167,000	30,924,000	30,652,000	30,158,000	29,783,000	30,829,000	[1]	30,420,000	[1]	28,636,000	[1]
Diluted earnings (loss) per share	$ 0.48	$ 0.52	$ 0.54	$ 0.40	$ 0.52	$ 0.54	$ 0.45	$ 0.37	$ 1.93	[1]	$ 1.88	[1]	$ (1.20)	[1]
Antidilutive shares attributable to stock-based awards outstanding excluded from computation of diluted earnings per share									36,501		122,263

[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 all performance-based awards underlying the 2014 awards in the 2014 calculation as the performance conditions for those awards were not met as of the end of the period. The Company has included the shares underlying the 2013 and 2012 awards in the respective year calculations, as those shares were contingently issuable upon the satisfaction of the annual targets consisting of net revenue, non-GAAP operating earnings and achievement of strategic goals as of the end of the periods.