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Common Stock - Issued and Outstanding Shares - Additional Information (Detail) - USD ($) |  |  |  |  |  |  |  |  |  | 12 Months Ended | 28 Months Ended
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Mar. 12, 2020 | Dec. 31, 2019 | Dec. 17, 2019 | Jun. 07, 2019 | Oct. 03, 2018 | Jun. 19, 2018 | Jun. 15, 2018 | May 22, 2018 | Sep. 14, 2017 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, par value |  | $ 0.001 |  |  |  |  |  |  |  | $ 0.001 | $ 0.001 |  | $ 0.001
Exercise price per unit of warrant |  |  |  |  |  | $ 4.00 |  |  |  |  |  |  |
Common stock, shares issued |  | 29,485,178 |  |  |  |  |  |  |  | 29,485,178 | 6,721,117 |  | 29,485,178
Preferred stock, par value |  | $ 0.001 |  |  |  |  |  |  |  | $ 0.001 |  |  | $ 0.001
Warrant exercisable period |  |  |  |  |  | 5 years |  |  |  |  |  |  |
Cancellation of warrant description |  |  |  |  |  |  |  |  |  | Additionally, subject to certain exceptions, if, after the June 19, 2018, (i) the volume weighted average price of our common stock for each of 30 consecutive trading days, or the 2018 Measurement Period, which 2018 Measurement Period commences on June 19, 2018, exceeds 300% of the exercise price (subject to adjustments for stock splits, recapitalizations, stock dividends and similar transactions), (ii) the average daily trading volume for such 2018 Measurement Period exceeds $500,000 per trading day and (iii) certain other equity conditions are met, and subject to a beneficial ownership limitation, then we may call for cancellation of all or any portion of the warrants then outstanding. |  |  |
Number of required consecutive days weighted average trading price for cancelation or recall of warrants |  |  |  |  |  | 30 days |  |  |  |  |  |  |
Minimum required trading price percentage over exercise price for cancelation or recall of warrants |  |  |  |  |  | 300.00% |  |  |  |  |  |  |
Minimum required trading volume value per day for cancelation or recall of warrants |  |  |  |  |  | $ 500,000 |  |  |  |  |  |  |
Gross proceeds from sale of warrants and units |  |  |  |  |  |  |  |  |  | $ 13,800,000 |  |  |
Warrant and units offering cost including underwriting discounts and commissions |  |  |  |  |  |  |  |  |  | 1,600,000 |  |  |
Net proceeds from issuance of warrants and units |  |  |  |  |  |  |  |  |  | $ 12,200,000 |  |  |
Proceeds from issuance of common stock |  |  |  |  |  |  |  |  |  |  |  | $ 64,000 |
Stock option exercises, Shares |  |  |  |  |  |  |  |  |  | 0 | 0 |  |
Restricted stock unit settlements |  |  |  |  |  |  |  |  |  | 5,134 | 5,354 |  |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Restricted stock unit settlements |  |  |  |  |  |  |  |  |  | 5,084 | 5,354 | 546 |
Direct Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Gross proceeds from issuance of common stock |  |  |  |  | $ 5,600,000 |  |  |  |  |  |  |  |
Placement agent fees and offering expenses |  |  |  |  | 600,000 |  |  |  |  |  |  |  |
Proceeds from issuance of common stock |  |  |  |  | $ 5,000,000 |  |  |  |  |  |  |  |
Direct Offering [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued |  |  |  |  | 1,789,258 |  |  |  |  |  | 1,789,258 |  |
Common stock, price per share |  |  |  |  | $ 3.1445 |  |  |  |  |  |  |  |
Private Placement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price per unit of warrant |  |  |  |  | $ 3.1445 |  |  |  |  |  |  |  |
Warrant exercisable period |  |  |  |  | 5 years |  |  |  |  |  |  |  |
Maximum number of common shares issuable per warrant upon conversion |  |  |  |  | 0.5 |  |  |  |  |  |  |  |
December 2019 Public Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price per unit of warrant |  |  | $ 0.60 |  |  |  |  |  |  |  |  |  |
Warrant exercisable period |  |  | 5 years |  |  |  |  |  |  |  |  |  |
Cancellation of warrant description |  |  |  |  |  |  |  |  |  | Additionally, subject to certain exceptions, if, after December 17, 2019, (i) the volume weighted average price of the common stock for each of 30 consecutive trading days, or the 2019 Measurement Period, which 2019 Measurement Period commences on the closing date, exceeds 300% of the exercise price (subject to adjustments for stock splits, recapitalizations, stock dividends and similar transactions), (ii) the average daily trading volume for such 2019 Measurement Period exceeds $500,000 per trading day and (iii) certain other equity conditions are met, and subject to a beneficial ownership limitation, then the Company may call for cancellation of all or any portion of the warrants then outstanding. |  |  |
Number of required consecutive days weighted average trading price for cancelation or recall of warrants |  |  | 30 days |  |  |  |  |  |  |  |  |  |
Minimum required trading price percentage over exercise price for cancelation or recall of warrants |  |  | 300.00% |  |  |  |  |  |  |  |  |  |
Minimum required trading volume value per day for cancelation or recall of warrants |  |  | $ 500,000 |  |  |  |  |  |  |  |  |  |
Gross proceeds from sale of warrants and units |  |  |  |  |  |  |  |  |  | $ 13,800,000 |  |  |
Warrant and units offering cost including underwriting discounts and commissions |  |  |  |  |  |  |  |  |  | 1,500,000 |  |  |
Net proceeds from issuance of warrants and units |  |  |  |  |  |  |  |  |  | $ 12,300,000 |  |  |
December 2019 Public Offering [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price per unit of warrant |  |  | $ 0.06 |  |  |  |  |  |  |  |  |  |
Series A Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value |  | $ 0.001 |  |  |  |  |  |  |  | $ 0.001 | $ 0.001 |  | $ 0.001
Preferred stock, shares converted |  | 9,158 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding |  | 0 |  |  |  |  |  |  |  | 0 | 579 |  | 0
Series A Convertible Preferred Stock [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible preferred stock, shares issued upon conversion |  | 2,289,500 |  |  |  |  |  |  |  |  |  |  |
Series B Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value |  | $ 0.001 |  |  |  |  |  |  |  | $ 0.001 | $ 0.001 |  | $ 0.001
Preferred stock, shares outstanding |  | 1,121 |  |  |  |  |  |  |  | 1,121 | 0 |  | 1,121
Series B Convertible Preferred Stock [Member] | December 2019 Public Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares converted |  |  |  |  |  |  |  |  |  | 5,135 |  |  |
Preferred stock, shares outstanding |  | 1,121 |  |  |  |  |  |  |  | 1,121 |  |  | 1,121
Series B Convertible Preferred Stock [Member] | December 2019 Public Offering [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible preferred stock, shares issued upon conversion |  |  |  |  |  |  |  |  |  | 8,554,910 |  |  |
Class A Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of new units in a public offering |  |  |  |  |  | 710,500 |  |  |  |  |  |  |
Public offering, price per unit |  |  |  |  |  | $ 4.00 |  |  |  |  |  |  |
Description of stock units issued |  |  |  |  |  |  |  |  |  | Each Class A Unit consisted of one share of our common stock and a warrant to purchase one share of common stock. |  |  |
Class A Units [Member] | December 2019 Public Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of new units in a public offering |  |  | 9,577,504 |  |  |  |  |  |  |  |  |  |
Public offering, price per unit |  |  | $ 0.60 |  |  |  |  |  |  |  |  |  |
Description of stock units issued |  |  |  |  |  |  |  |  |  | Each Class A Unit consisted of one share of our common stock and a warrant to purchase one share of common stock. |  |  |
Class B Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of new units in a public offering |  |  |  |  |  | 9,158 |  |  |  |  |  |  |
Public offering, price per unit |  |  |  |  |  | $ 1,000 |  |  |  |  |  |  |
Description of stock units issued |  |  |  |  |  |  |  |  |  | Each Class B Unit consisted of one share of Series A Convertible Preferred Stock, par value $0.001 per share, convertible at any time at the holder’s option into 250 shares of common stock and warrants to purchase 250 shares of common stock. |  |  |
Number of common shares issuable for each share of convertible preferred stock |  |  |  |  |  | 250 |  |  |  |  |  |  |
Number of common shares issuable conversion of warrants |  |  |  |  |  | 250 |  |  |  |  |  |  |
Class B Units [Member] | December 2019 Public Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance of new units in a public offering |  |  | 6,256 |  |  |  |  |  |  |  |  |  |
Public offering, price per unit |  |  | $ 999.60 |  |  |  |  |  |  |  |  |  |
Description of stock units issued |  |  |  |  |  |  |  |  |  | Each Class B Unit consisted of one share of Series B Convertible Preferred Stock, par value $0.001 per share, convertible at any time at the holder’s option into 1,666 shares of common stock, and warrants to purchase 1,666 shares of common stock. |  |  |
Number of common shares issuable for each share of convertible preferred stock |  |  | 1,666 |  |  |  |  |  |  |  |  |  |
Number of common shares issuable conversion of warrants |  |  | 1,666 |  |  |  |  |  |  |  |  |  |
Class B Units [Member] | Series A Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value |  |  |  |  |  | $ 0.001 |  |  |  |  |  |  |
Class B Units [Member] | Series A Convertible Preferred Stock [Member] | December 2019 Public Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value |  |  | $ 0.001 |  |  |  |  |  |  |  |  |  |
LPC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum percentage of common stock shares outstanding authorized to sell |  |  |  |  |  |  |  | 20.00% |  |  |  |  |
Initial purchase of common stock |  |  |  |  |  |  |  |  |  |  |  |  | 32,895
Common stock, shares issued |  |  |  |  |  |  |  |  | 12,352 |  |  |  |
Common stock, shares issued |  |  |  |  |  |  |  |  |  | 374,000 |  |  | 557,378
Gross proceeds |  |  |  |  |  |  |  |  |  | $ 800,000 |  |  | $ 4,400,000
Offering expenses |  |  |  |  |  |  |  |  |  |  |  |  | 500,000
LPC [Member] | Purchase Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, purchase price |  |  |  |  |  |  |  |  | $ 1.00 |  |  |  |
Additional common stock value right to sell, maximum |  |  |  |  |  |  |  |  | $ 10,000,000 |  |  |  |
Additional purchase of common stock, maximum |  |  |  |  |  |  |  |  | 150,000 |  |  |  |
LPC [Member] | Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Initial purchase of common stock |  |  |  |  |  |  |  |  | 32,895 |  |  |  |
Common stock, purchase price |  |  |  |  |  |  |  |  | $ 30.40 |  |  |  |
Purchase agreement, description |  |  |  |  |  |  |  |  |  | Unit consisting of (a) one share of our common stock and (b) one warrant to purchase one-quarter of a share of common stock at an exercise price of $34.96 per share, or Warrant. Each Warrant became exercisable six months following the issuance date until the date that is five years and six months after the issuance date and is subject to customary adjustments. |  |  |
Exercise price per unit of warrant |  |  |  |  |  |  |  |  | $ 34.96 |  |  |  |
Initial purchase of units consisting of common stock and warrants issued |  |  |  |  |  |  |  |  | $ 1,000,000 |  |  |  |
LPC [Member] | Other Units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Number of warrants issued |  |  |  |  |  |  |  |  | 0 |  |  |  |
LPC [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock value right to sell, maximum | $ 11,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Common stock, par value | $ 0.001 |  |  |  |  |  |  |  |  |  |  |  |
LPC [Member] | Subsequent Event [Member] | Purchase Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Payments related to expense reimbursement | $ 100,000 |  |  |  |  |  |  |  |  |  |  |  |
Ladenburg Thalmann & Co. Inc [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Period granted for underwriting option |  |  | 45 days |  |  |  | 45 days |  |  |  |  |  |
Ladenburg Thalmann & Co. Inc [Member] | 2018 Overallotment Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Additional purchase of common stock and warrants, maximum |  |  |  |  |  |  | 450,000 |  |  |  |  |  |
Overallotment option exercise date |  |  |  |  |  |  | Jun. 18, 2018 |  |  |  |  |  |
Ladenburg Thalmann & Co. Inc [Member] | 2019 Overallotment Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Additional purchase of common stock and warrants, maximum |  |  | 3,000,000 |  |  |  |  |  |  |  |  |  |
Overallotment option exercise date |  |  | Dec. 17, 2019 |  |  |  |  |  |  |  |  |  |
H.C. Wainwright [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, par value |  |  |  | $ 0.001 |  |  |  |  |  |  |  |  |
Percentage of commission on gross proceeds from sale of common stock |  |  |  | 3.00% |  |  |  |  |  |  |  |  |
Common stock available for sale under offering |  | $ 6,000,000 |  |  |  |  |  |  |  | $ 6,000,000 |  |  | $ 6,000,000
H.C. Wainwright [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock value right to sell, maximum |  |  |  | $ 6,000,000 |  |  |  |  |  |  |  |  |

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