INCOME TAXES - Income tax effect of temporary differences comprising the deferred tax assets and deferred tax liabilities (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Net operating loss carryforwards	$ 91,118	$ 86,848
Tax credit carryforwards	22,172	22,492
Equity based compensation	6,774	5,881
Book depreciation in excess of tax	2,263	2,321
Reserves and accruals	(132)	(101)
Deferred revenue	15,672	21,439
Loss on investment	194	194
Other	140	180
Deferred tax assets, gross	138,201	139,254
Valuation allowance	(138,201)	(139,254)
Deferred tax liabilities
Net deferred tax assets