CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total		Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Balances at beginning of period at Dec. 31, 2018	$ 29,371		$ 6	$ 295,116	$ (264,713)	$ (1,038)
Balances at beginning of period (in shares) at Dec. 31, 2018			5,938
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through equity distribution agreement, net of offering costs	$ 1,504		$ 1	1,503	0	0
Issuance of common stock through equity distribution agreement, net of offering costs (in shares)	570		570
Issuance of common stock from vesting of restricted stock units	$ 0		$ 0	0	0	0
Issuance of common stock from vesting of restricted stock units (in shares)			92
Tax withholding related to vesting of restricted stock units	(254)		$ 0	(254)	0	0
Issuance of common stock under employee stock purchase plan	88		$ 0	88	0	0
Issuance of common stock under employee stock purchase plan (in shares)			42
Stock-based compensation expense	2,100		$ 0	2,100	0	0
Net loss	(11,882)		0	0	(11,882)	0
Foreign currency translation adjustments	(49)		0	0	0	(49)
Balances at end of period at Sep. 30, 2019	20,878		$ 7	298,553	(276,595)	(1,087)
Balances at end of period (in shares) at Sep. 30, 2019			6,642
Balances at beginning of period at Dec. 31, 2018	29,371		$ 6	295,116	(264,713)	(1,038)
Balances at beginning of period (in shares) at Dec. 31, 2018			5,938
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(12,408)
Balances at end of period at Dec. 31, 2019	21,060	[1]	$ 7	299,263	(277,112)	(1,098)
Balances at end of period (in shares) at Dec. 31, 2019			6,810
Balances at beginning of period at Jun. 30, 2019	23,555		$ 7	297,903	(273,322)	(1,033)
Balances at beginning of period (in shares) at Jun. 30, 2019			6,623
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from vesting of restricted stock units	0		$ 0	0	0	0
Issuance of common stock from vesting of restricted stock units (in shares)			19
Tax withholding related to vesting of restricted stock units	(3)		$ 0	(3)	0	0
Stock-based compensation expense	653		0	653	0	0
Net loss	(3,273)		0	0	(3,273)	0
Foreign currency translation adjustments	(54)		0	0	0	(54)
Balances at end of period at Sep. 30, 2019	20,878		$ 7	298,553	(276,595)	(1,087)
Balances at end of period (in shares) at Sep. 30, 2019			6,642
Balances at beginning of period at Dec. 31, 2019	21,060	[1]	$ 7	299,263	(277,112)	(1,098)
Balances at beginning of period (in shares) at Dec. 31, 2019			6,810
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through equity distribution agreement, net of offering costs	$ 179		$ 0	179	0	0
Issuance of common stock through equity distribution agreement, net of offering costs (in shares)	134		134
Issuance of common stock from vesting of restricted stock units	$ 0		$ 0	0	0	0
Issuance of common stock from vesting of restricted stock units (in shares)			160
Tax withholding related to vesting of restricted stock units	(174)		$ 0	(174)	0	0
Issuance of common stock under employee stock purchase plan	14		$ 0	14	0	0
Issuance of common stock under employee stock purchase plan (in shares)			11
Stock-based compensation expense	1,208		$ 0	1,208	0	0
Net loss	(11,524)		0	0	(11,524)	0
Foreign currency translation adjustments	47		0	0	0	47
Balances at end of period at Sep. 30, 2020	10,810		$ 7	300,490	(288,636)	(1,051)
Balances at end of period (in shares) at Sep. 30, 2020			7,115
Balances at beginning of period at Jun. 30, 2020	14,572		$ 7	300,139	(284,564)	(1,010)
Balances at beginning of period (in shares) at Jun. 30, 2020			6,959
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through equity distribution agreement, net of offering costs	$ 179		$ 0	179	0	0
Issuance of common stock through equity distribution agreement, net of offering costs (in shares)	134		134
Issuance of common stock from vesting of restricted stock units	$ 0		$ 0	0	0	0
Issuance of common stock from vesting of restricted stock units (in shares)			22
Tax withholding related to vesting of restricted stock units	(23)		$ 0	(23)	0	0
Stock-based compensation expense	195		0	195	0	0
Net loss	(4,072)		0	0	(4,072)	0
Foreign currency translation adjustments	(41)		0	0	0	(41)
Balances at end of period at Sep. 30, 2020	$ 10,810		$ 7	$ 300,490	$ (288,636)	$ (1,051)
Balances at end of period (in shares) at Sep. 30, 2020			7,115

[1] Derived from the Company’s audited consolidated financial statements as of December 31, 2019.