EMPLOYEE STOCK PLANS - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Outstanding, beginning balance (in shares)	4,920	4,993
Granted (in shares)	716	746	1,600
Exercised (in shares)	(1,017)	(486)
Forfeited or expired (in shares)	(447)	(333)
Outstanding, ending balance (in shares)	4,172	4,920	4,993
Vested and expected to vest (in shares)	3,928
Exercisable (in shares)	2,785
Weighted-Average Exercise Price
Weighted-Average Exercise Price Per Share, beginning balance (in usd per share)	$ 2.01	$ 2.18
Weighted Average Exercise Price Per Share, Granted (in usd per share)	3.37	2.42
Weighted Average Exercise Price Per Share, Exercised (in usd per share)	1.91	1.03
Weighted Average Exercise Price Per Share, Forfeited or expired (in usd per share)	4.16	7.01
Weighted-Average Exercise Price Per Share, ending balance (in usd per share)	2.04	$ 2.01	$ 2.18
Weighted Average Exercise Price, Vested and expected to vest (in usd per share)	2.00
Weighted Average Exercise Price, Exercisable (in usd per share)	$ 1.80
Weighted Average Remaining Term
Weighted Average Remaining Contractual Life	4 years 1 month 15 days	4 years 2 months 12 days	4 years 10 months 24 days
Weighted Average Remaining Contractual Life, Vested and expected to vest	4 years
Weighted Average Remaining Contractual Life, Exercisable	3 years 6 months
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 6,254	$ 7,513	$ 5,281
Aggregate Intrinsic Value, Vested and expected to vest	6,059
Aggregate Intrinsic Value, Exercisable	$ 4,818