Statements of Stockholders’ Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2016	$ 1	$ 123,309	$ (96,439)	$ 26,871
Balance (in shares) at Dec. 31, 2016	12,498,128
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options		1,337		1,337
Issuance of common stock upon exercise of stock options (in shares)	281,483
Issuance of common stock under Employee Stock Purchase Plan		256		256
Issuance of common stock under Employee Stock Purchase Plan (in shares)	37,590
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES		1,472		1,472
Stock-based compensation expense		2,048		2,048
Net loss			(21,100)	(21,100)
Balance at Dec. 31, 2017	$ 1	128,422	(117,539)	10,884
Balance (in shares) at Dec. 31, 2017	12,817,201
Increase (Decrease) in Stockholders' Equity
Adjustment to opening balance for adoption of new accounting standard			1,300	1,300
Issuance of common stock in secondary offering, net of issuance costs	$ 1	24,523		24,524
Issuance of common stock in secondary offering, net of issuance costs (in shares)	3,772,447
Issuance of common stock under stock incentive plans		2,503		$ 2,503
Issuance of common stock under stock incentive plans (in shares)	505,808
Issuance of common stock upon exercise of stock options (in shares)				448,411
Issuance of warrant		43		$ 43
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES		753		753
Stock-based compensation expense		2,668		2,668
Net loss			(17,754)	(17,754)
Balance at Dec. 31, 2018	$ 2	$ 158,912	$ (133,993)	$ 24,921
Balance (in shares) at Dec. 31, 2018	17,095,456