EMPLOYEE STOCK PLANS - Stock Option Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Number of Shares
Outstanding at December 31, 2012 (in shares)	7,614
Granted (in shares)	1,399
Exercised (in shares)	(243)
Canceled or forfeited (in shares)	(2,799)
Outstanding at June 30, 2013 (in shares)	5,971
Vested and expected to vest at June 30, 2013 (in shares)	5,384
Exercisable at June 30, 2013 (in shares)	2,392
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Outstanding at December 31, 2012 (in usd per share)	$ 3.34
Weighted Average Exercise Price, Granted (in usd per share)	$ 1.28
Weighted Average Exercise Price, Exercised (in usd per share)	$ 0.85
Weighted Average Exercise Price, Canceled or forfeited (in usd per share)	$ 4.34
Weighted-Average Exercise Price, Outstanding at June 30, 2013 (in usd per share)	$ 2.48
Weighted Average Exercise Price, Vested and expected to vest at June 30, 2013 (in usd per share)	$ 2.60
Weighted Average Exercise Price, Exercisable at June 30, 2013 (in usd per share)	$ 4.09
Weighted Average Remaining Term
Weighted Average Remaining Term, Outstanding at June 30, 2013	4 years 10 months 28 days
Weighted Average Remaining Term, Vested and expected to vest at June 30, 2013	4 years 7 months 9 days
Weighted Average Remaining Term, Exercisable at June 30, 2013	3 years
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding at June 30, 2013	$ 3,781
Aggregate Intrinsic Value, Vested and expected to vest at June 30, 2013	3,290
Aggregate Intrinsic Value, Exercisable at June 30, 2013	$ 630