Income taxes (Deferred Tax Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets, current
Reserves	$ 2,581	$ 2,526
Other	749	617
Total gross deferred tax assets, current	3,330	3,143
Deferred tax assets, noncurrent
Net operating loss carryforwards	122,281	116,520
R&D credit carryforwards	6,747	6,520
Depreciation/amortization deferred	20,848	22,642
Other	7,954	7,846
Total gross deferred tax assets, noncurrent	157,830	153,528
Net deferred taxes before valuation allowance	161,160	156,671
Less: Valuation allowance	(161,160)	(156,671)
Deferred tax assets	$ 0	$ 0