Income Taxes (Deferred tax assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net operating loss carryforward	$ 32,723	$ 29,798
Research and development credits	8,449	6,840
Deferred Tax Assets, Property, Plant and Equipment	2,402	3,007
Reserves and accruals	9,349	9,661
Total deferred tax assets	52,923	49,306
Valuation allowance	(40,436)	(40,070)	$ (45,255)	$ (42,339)
Net deferred tax assets	12,487	9,236
Deferred tax liabilities - convertible senior notes	(5,848)	(7,503)
Deferred tax liabilities - other	(7,097)	(2,208)
Net deferred tax liabilities	(458)	(475)
Deferred tax assets (increase) decrease	$ (400)	$ 5,200