Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
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	24,608		24,609
Issuance of common stock in secondary offering, net of issuance costs (in shares)	3,772,447
Issuance of common stock under stock incentive plans		309		309
Issuance of common stock under stock incentive plans (in shares)	58,229
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES		237		237
Stock-based compensation expense		625		625
Net loss			(1,277)	(1,277)
Balance at Mar. 31, 2018	$ 2	154,201	(117,516)	36,687
Balance (in shares) at Mar. 31, 2018	16,647,877
Balance at Dec. 31, 2018	$ 2	158,912	(133,993)	24,921
Balance (in shares) at Dec. 31, 2018	17,095,456
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans		13		13
Issuance of common stock under stock incentive plans (in shares)	12,607
Stock-based compensation expense		704		704
Net loss			(4,256)	(4,256)
Balance at Mar. 31, 2019	$ 2	$ 159,629	$ (138,249)	$ 21,382
Balance (in shares) at Mar. 31, 2019	17,108,063