Stockholders' Equity - Company's Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2021	Dec. 31, 2020
OUTSTANDING OPTIONS
Outstanding at beginning of period	100,600
Options forfeited	(24,508)
Outstanding at end of period		100,600
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period	$ 3.09
Options forfeited	$ 2.06
Outstanding at end of period		$ 3.09
ADDITIONAL DISCLOSURES
Outstanding options exercisable at end of period	11,967
Weighted-average exercise price exercisable at end of period	$ 2.06
Weighted-average contractual term (years) exercisable	1 year 7 months 6 days	9 years 6 months
Aggregate intrinsic value (in thousands) exercisable at end of period	$ 3
2003 Stock Incentive Plan
OUTSTANDING OPTIONS
Outstanding at beginning of period	97,250
Options exercised	(3,785)
Outstanding at end of period	93,465	97,250
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period	$ 1.96
Options granted	1.12
Outstanding at end of period	$ 2.00	$ 1.96
VESTED AND EXPECTED TO VEST
Weighted-Average Remaining Contractual Term	9 months 18 days	1 year 3 months 18 days
Aggregate Intrinsic Value (in thousands)	$ 31
2013 Equity Incentive Plan
OUTSTANDING OPTIONS
Outstanding at beginning of period	5,753,211
Options granted	898,100
Options exercised	0
Options forfeited	(815,132)
Outstanding at end of period	5,836,179	5,753,211
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period	$ 8.93
Options granted	3.70
Options forfeited	8.32
Outstanding at end of period	$ 8.22	$ 8.93
VESTED AND EXPECTED TO VEST
Outstanding options	5,836,179
Weighted-Average Exercise Price	$ 8.22
Weighted-Average Remaining Contractual Term	6 years 9 months 18 days
ADDITIONAL DISCLOSURES
Outstanding options exercisable at end of period	4,128,319
Weighted-average exercise price exercisable at end of period	$ 9.17
Weighted-average contractual term (years) exercisable	5 years 2 months 12 days
Weighted-average contractual term outstanding	6 years 9 months 18 days	6 years 7 months 6 days

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