Income Taxes - Deferred Income Taxes Components (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforward	$ 42,013	$ 28,584
Property & equipment	690	339
Inventory	1,735	864
Stock options	7,208	5,208
Intangible assets, definite-lived	220	333
General business credit	3,984	1,915
Deferred revenue	370	372
Other	121	205
Valuation allowance	(56,341)	(37,820)
Deferred tax assets	$ 0	$ 0