NET INCOME (LOSS) PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income (loss)	$ 7,006	$ (911)	$ 11,392	$ (11,385)
Interest on convertible notes	1,191		2,381
Adjusted net income (loss)	$ 8,197	$ (911)	$ 13,773	$ (11,385)
Shares used in computing basic net income (loss) per common share	78,476	72,944	76,951	72,722
Employee stock options	1,559		1,604
Employee stock purchase plan	4		3
Restricted stock and restricted stock units	1,566		1,604
Convertible notes	17,857		17,857
Shares used in computing diluted net income (loss) per common share (in shares)	99,462	72,944	98,019	72,722
Basic net income (loss) per common share (in usd per share)	$ 0.09	$ (0.01)	$ 0.15	$ (0.16)
Diluted net income (loss) per common share (in usd per share)	$ 0.08	$ (0.01)	$ 0.14	$ (0.16)