Stockholders' Equity - Transactions with Oasis Capital and Underwritten Public Offering (Details)								1 Months Ended				2 Months Ended	12 Months Ended		14 Months Ended
	Dec. 10, 2021 shares	Apr. 29, 2021 USD ($) $ / shares shares	Jan. 13, 2021 USD ($) $ / shares	Oct. 06, 2020 USD ($) $ / shares shares	Oct. 05, 2020 USD ($) shares	Mar. 23, 2020 USD ($) $ / shares	Mar. 05, 2020 USD ($) $ / shares	Dec. 31, 2021 USD ($) shares	Apr. 30, 2020 USD ($) shares	Mar. 31, 2020 USD ($) D $ / shares shares	Feb. 29, 2020 USD ($) $ / shares	Feb. 28, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Feb. 28, 2021 shares	Mar. 10, 2022 shares	Apr. 07, 2021 $ / shares shares	Apr. 06, 2021 $ / shares	Apr. 15, 2020 USD ($)	Mar. 22, 2020 $ / shares	Mar. 04, 2020 $ / shares	Jan. 31, 2020 $ / shares	Dec. 31, 2019 USD ($)	Sep. 30, 2019 $ / shares	Aug. 31, 2019 $ / shares	Jul. 31, 2019 $ / shares	Aug. 28, 2018 shares
Stockholders' equity								$ 11,853,000					$ 11,853,000	$ 17,202,000									$ 10,673,000
Number of securities issued on conversion | shares																											9,580
Common stock, shares issued | shares																28,701,463
Proceeds from exercise of warrants													1,776,000	6,057,000
Share Price | $ / shares										$ 1.31
PoC Capital, LLC
Share Price | $ / shares				$ 0.90
Registered Direct Offering
Number of shares offered | shares		2,549,000
Gross proceeds from the issuance of common stock		$ 10,800,000
Amount of shares issued														1,207,000
Share Price | $ / shares		$ 4.23
Issuance costs		$ 948,000											2,550,000
At The Market Offering
Amount of shares issued													8,595,000
Issuance costs													465,000	$ 78,000
October 2020 ATM Agreement
Issuance of common stock (In shares) | shares					1,271,639										669,850
Issuance costs					$ 40,000							$ 311,000
Sale of worth of shares					$ 1,300,000							$ 5,400,000
December 2021 ATM Agreement
Gross proceeds from issuance								$ 3,200,000
Issuance of common stock (In shares) | shares								2,261,596
December 2021 ATM Agreement | Maximum
Number of shares offered | shares	15,000,000.0
Series 1 warrants
Exercise price (in dollars per share) | $ / shares											$ 2.08											$ 6.00		$ 4.20	$ 6.00	$ 6.00
Proceeds from issuance of warrants											$ 144,000		682,000
Series 2 warrants
Exercise price (in dollars per share) | $ / shares						$ 1.57	$ 1.82			$ 6.00										$ 6.00	$ 6.00					$ 6.00
Class of Warrant or Right Exercised | shares										416,666
Proceeds from issuance of warrants							$ 55,000						$ 700,000
Net proceeds from issuance of warrants						$ 628,000
Issuance costs						$ 25,000
PIPE Financing Warrants, March 2020
Proceeds from issuance of warrants										$ 720,000
Net proceeds from issuance of warrants										668,000
Issuance costs										$ 52,000
PIPE Financing Warrants, March 2020 | Private placement
Issuance of common stock (In shares) | shares										571,427
Securities purchase agreement | Registered Direct Offering
Amount of shares issued			$ 1,479,290
Share Price | $ / shares			$ 10.14
Net proceeds			$ 1,600,000
Proceeds from issuance of warrants			$ 15,000,000.0
Equity Line of Credit
Price per share | $ / shares																	$ 9.00	$ 1.31
Gross proceeds from issuance									$ 23,000
Number of securities issued on conversion | shares																	33,333
Exercise price | $ / shares																	$ 5.61
Amount of shares issued										$ 200,000
Par value (per share) | $ / shares																	$ 10.35	$ 1.50
Term of equity purchase agreement										36 months
Shares issued in settlement of commitment fee | shares									22,935
Fair value of equity issued									$ 33,000
Equity Line of Credit | Maximum
Aggregate amount of put option on any put date or clearing date										$ 500,000
Aggregate amount of equity purchase agreement										$ 2,000,000.0
Stock Plan Agreement with Poc LLc | PoC Capital, LLC
Issuance of common stock (In shares) | shares				444,444
Share Price | $ / shares				$ 0.90
Napo | PoC Capital, LLC
Amount of shares issued				$ 400,000
Napo | Stock Plan Agreement with Poc LLc | PoC Capital, LLC
Amount of shares issued				$ 400,000
Option 1 Put | Equity Line of Credit
Issuance of common stock (In shares) | shares									17,333	66,666
Percentage of average trading volume										20.00%
Trading days | D										10
Option 2 Puts | Equity Line of Credit
Percentage of average trading volume										10.00%
Share Price | $ / shares										$ 1.31
Option 1 and Option 2 Puts | Equity Line of Credit
Stockholders' equity																			$ 0
Derivative Asset, Noncurrent																			$ 0