INCOME TAXES - Temporary differences to the components of deferred tax assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current deferred tax assets:
Inventory	$ 323	$ 289
Accrued compensation	251	237
Net operating loss carryforwards domestic	52	1,151
Other	1,252	862
Deferred tax asset before valuation current	1,878	2,539
Valuation allowance	(748)	(1,369)
Total current deferred tax assets	1,130	1,170
Noncurrent deferred tax assets:
Research and development tax credit	526	553
Alternative minimum tax credit	232	228
Deferred revenue	1,884	1,840
Property and equipment	2,059	1,932
Net operating loss carryforwards domestic	39,533	52,456
Deferred tax asset before valuation noncurrent	44,234	57,009
Valuation allowance	(17,603)	(29,875)
Total noncurrent deferred tax assets	$ 26,746	$ 27,134