Condensed Statements of Stockholders' Equity - USD ($)	At-the-Market Sales Agreement Common Stock	At-the-Market Sales Agreement Additional Paid-In Capital	At-the-Market Sales Agreement	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2017				$ 1,000	$ 128,422,000	$ (117,539,000)	$ 10,884,000
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						1,300,000	1,300,000
Issuance of common stock in at-the-market offering				$ 1,000	24,608,000		24,609,000
Issuance of common stock in at-the-market offering (in shares)				3,772,447
Issuance of common stock under stock incentive plans					309,000		309,000
Issuance of common stock under stock incentive plans (in shares)				58,229
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES					237,000		237,000
Stock-based compensation expense					625,000		625,000
Net loss						(1,277,000)	(1,277,000)
Balance at Mar. 31, 2018				$ 2,000	154,201,000	(117,516,000)	36,687,000
Balance (in shares) at Mar. 31, 2018				16,647,877
Balance at Dec. 31, 2017				$ 1,000	128,422,000	(117,539,000)	10,884,000
Balance (in shares) at Dec. 31, 2017				12,817,201
Increase (Decrease) in Stockholders' Equity
Net loss							(14,274,000)
Balance at Sep. 30, 2018				$ 2,000	158,125,000	(130,514,000)	27,613,000
Balance (in shares) at Sep. 30, 2018				17,065,846
Balance at Mar. 31, 2018				$ 2,000	154,201,000	(117,516,000)	36,687,000
Balance (in shares) at Mar. 31, 2018				16,647,877
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans					723,000		723,000
Issuance of common stock under stock incentive plans (in shares)				152,628
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES					225,000		225,000
Stock-based compensation expense					717,000		717,000
Net loss						(7,369,000)	(7,369,000)
Balance at Jun. 30, 2018				$ 2,000	155,866,000	(124,885,000)	30,983,000
Balance (in shares) at Jun. 30, 2018				16,800,505
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans					1,332,000		1,332,000
Issuance of common stock under stock incentive plans (in shares)				265,341
Issuance of warrant					43,000		43,000
Secondary offering issuance costs					(85,000)		(85,000)
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES					247,000		247,000
Stock-based compensation expense					722,000		722,000
Net loss						(5,629,000)	(5,629,000)
Balance at Sep. 30, 2018				$ 2,000	158,125,000	(130,514,000)	27,613,000
Balance (in shares) at Sep. 30, 2018				17,065,846
Balance at Dec. 31, 2018				$ 2,000	158,912,000	(133,993,000)	24,921,000
Balance (in shares) at Dec. 31, 2018				17,095,456
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans					13,000		13,000
Issuance of common stock under stock incentive plans (in shares)				12,607
Stock-based compensation expense					704,000		704,000
Net loss						(4,256,000)	(4,256,000)
Balance at Mar. 31, 2019				$ 2,000	159,629,000	(138,249,000)	21,382,000
Balance (in shares) at Mar. 31, 2019				17,108,063
Balance at Dec. 31, 2018				$ 2,000	158,912,000	(133,993,000)	24,921,000
Balance (in shares) at Dec. 31, 2018				17,095,456
Increase (Decrease) in Stockholders' Equity
Issuance of common stock in at-the-market offering (in shares)			377,115
Net loss							(11,589,000)
Balance at Sep. 30, 2019				$ 2,000	163,640,000	(145,582,000)	18,060,000
Balance (in shares) at Sep. 30, 2019				17,535,746
Balance at Mar. 31, 2019				$ 2,000	159,629,000	(138,249,000)	21,382,000
Balance (in shares) at Mar. 31, 2019				17,108,063
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans					137,000		137,000
Issuance of common stock under stock incentive plans (in shares)				43,227
Stock-based compensation expense					798,000		798,000
Net loss						(3,670,000)	(3,670,000)
Balance at Jun. 30, 2019				$ 2,000	160,564,000	(141,919,000)	18,647,000
Balance (in shares) at Jun. 30, 2019				17,151,290
Increase (Decrease) in Stockholders' Equity
Issuance of common stock in at-the-market offering	$ 377,115	$ 2,172,000	$ 2,172,000
Issuance of common stock under stock incentive plans					28,000		28,000
Issuance of common stock under stock incentive plans (in shares)				7,341
Modification of warrant in conjunction with 2019 Credit Facility					(19,000)		(19,000)
Stock-based compensation expense					895,000		895,000
Net loss						(3,663,000)	(3,663,000)
Balance at Sep. 30, 2019				$ 2,000	$ 163,640,000	$ (145,582,000)	$ 18,060,000
Balance (in shares) at Sep. 30, 2019				17,535,746