Income taxes (Deferred Tax Assets) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets, current
Reserves	$ 2,994,000	$ 3,804,000
Other	621,000	710,000
Total gross deferred tax assets, current	3,615,000	4,514,000
Deferred tax assets, noncurrent
Net operating loss carryforwards	111,339,000	104,893,000
R&D credit carryforwards	6,277,000	6,032,000
Depreciation/amortization deferred	24,526,000	26,594,000
Other	7,544,000	7,573,000
Total gross deferred tax assets, noncurrent	149,686,000	145,092,000
Total gross deferred tax liabilities, noncurrent	0	0
Net deferred taxes before valuation allowance	153,301,000	149,606,000
Less: Valuation allowance	(153,301,000)	(149,606,000)
Deferred tax assets	$ 0	$ 0