Other balance sheet items - Schedule of Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (5,613)		$ (5,613)		$ (4,956)
Indefinite-lived Intangible Assets [Line Items]
Acquisition Cost	7,340		7,340		6,931
Carrying Value	1,727		1,727		1,975
Amortization expense for intangibles	200	$ 200	700	$ 700
Licenses
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	991		991		987
Strategic Alliance
Finite-Lived Intangible Assets [Line Items]
Acquisition Cost, Finite-lived Intangible Assets	3,717		3,717		3,748
Accumulated Amortization	(3,693)		(3,693)		(3,472)
Carrying Value, Finite-lived Intangible Assets	24		$ 24		276
Strategic Alliance | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life			3 years
Other
Finite-Lived Intangible Assets [Line Items]
Acquisition Cost, Finite-lived Intangible Assets	2,632		$ 2,632		2,196
Accumulated Amortization	(1,920)		(1,920)		(1,484)
Carrying Value, Finite-lived Intangible Assets	$ 712		$ 712		$ 712
Other | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life			3 years