STOCK-BASED COMPENSATION (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Stock-based compensation
Stock-based compensation expense	$ 885,000	$ 858,000	$ 2,460,000	$ 2,313,000
Additional disclosure
Total unrecognized compensation expense related to unvested stock-based awards	4,303,000		4,303,000
Weighted average period over which expense is expected to be recognized			2 years 6 months 4 days
Stock options
Weighted-average assumptions
Risk-free interest rate (as a percent)	1.21%	1.47%	1.27%	2.01%
Expected volatility (as a percent)	63.14%	59.01%	70.44%	58.51%
Expected life	6 years 7 months 13 days	6 years 3 months 7 days	6 years 3 months 11 days	5 years 11 months 12 days
Estimated forfeiture rates (as a percent)			7.47%	7.89%
Options Outstanding
Balance at the beginning of the period (in shares)			14,366,623
Granted (in shares)			2,305,170
Exercised (in shares)			(415,081)
Forfeited (in shares)			(251,949)
Expired (in shares)			(507,237)
Balance at the end of the period (in shares)	15,497,526		15,497,526
Vested or expected to vest at the end of the period (in shares)	14,882,686		14,882,686
Exercisable at the end of the period (in shares)	10,447,411		10,447,411
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)			$ 3.83
Granted (in dollars per share)			$ 1.85
Exercised (in dollars per share)			$ 1.35
Forfeited (in dollars per share)			$ 2.46
Expired (in dollars per share)			$ 3.84
Balance at the end of the period (in dollars per share)	$ 3.62		$ 3.62
Vested or expected to vest at the end of the period (in dollars per share)	$ 3.62		$ 3.62
Exercisable at the end of the period (in dollars per share)	$ 3.78		$ 3.78
Weighted Average Remaining Contractual Term
Balance at the end of the period			5 years 10 months 2 days
Vested or expected to vest at the end of the period			5 years 9 months 18 days
Exercisable at the end of the period			5 years 1 month 20 days
Aggregate Intrinsic Value
Balance at the end of the period	10,796,300		10,796,300
Vested or expected to vest at the end of the period	10,360,500		10,360,500
Exercisable at the end of the period	6,473,900		6,473,900
Additional disclosure
Weighted-average grant-date fair value of options granted (in dollars per share)			$ 1.18
Total intrinsic value of options exercised			528,000
Cash received from exercise of options			$ 560,000
Stock options | Minimum
Weighted-average assumptions
Period over which stock is not traded in market			1 year
Stock Option Plans
Stock-based compensation
Number of shares authorized for issuance	24,000,976		24,000,976
Stock Option Plans | Stock options
Stock-based compensation
Expiration term of options granted			10 years
Stock Option Plans | Stock options | Minimum
Stock-based compensation
Options granted vesting period			4 years
Stock Option Plans | Stock options | Maximum
Stock-based compensation
Options granted vesting period			5 years
Employee Stock Purchase Plan
Stock-based compensation
Purchase price expressed as percentage of fair market value of common stock			85.00%