Income taxes (Deferred Tax Assets) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets, current
Reserves	$ 3,804,000	$ 4,395,000
Other	710,000	806,000
Total gross deferred tax assets, current	4,514,000	5,201,000
Deferred tax assets, noncurrent
Net operating loss carryforwards	104,893,000	97,156,000
R&D credit carryforwards	6,032,000	5,754,000
Depreciation/amortization deferred	26,594,000	26,510,000
Other	7,573,000	6,958,000
Total gross deferred tax assets, noncurrent	145,092,000	136,378,000
Total gross deferred tax liabilities, noncurrent	0	0
Net deferred taxes before valuation allowance	149,606,000	141,579,000
Less: Valuation allowance	(149,606,000)	(141,579,000)
Deferred tax assets	$ 0	$ 0