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Common Stock - Issued and Outstanding Shares - Additional Information (Detail) - USD ($) |  |  |  |  |  |  |  | 3 Months Ended | 6 Months Ended | 23 Months Ended |  |
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Jun. 30, 2019 | Jun. 07, 2019 | Oct. 03, 2018 | Jun. 19, 2018 | Jun. 15, 2018 | May 22, 2018 | Sep. 14, 2017 | Jun. 30, 2019 | Mar. 31, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Aug. 08, 2019 | Dec. 31, 2018 | May 23, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, par value | $ 0.001 |  |  |  |  |  |  | $ 0.001 |  |  | $ 0.001 |  |  | $ 0.001 | $ 0.001
Exercise price per unit of warrant |  |  |  | $ 4.00 |  |  |  |  |  |  |  |  |  |  |
Initial purchase of units consisting of common stock and warrants issued |  |  |  |  |  |  |  |  |  |  | $ 423,000 | $ 1,280,000 |  |  |
Common stock, shares issued | 8,097,763 |  |  |  |  |  |  | 8,097,763 |  |  | 8,097,763 |  |  | 6,721,117 |
Preferred stock, par value | $ 0.001 |  |  |  |  |  |  | $ 0.001 |  |  | $ 0.001 |  |  | $ 0.001 |
Warrant exercisable period |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |
Cancellation of warrant description |  |  |  |  |  |  |  |  |  |  | Additionally, subject to certain exceptions, if, after June 19, 2018, (i) the volume weighted average price of our common stock for each of any 30 consecutive trading days, or the Measurement Period, which 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 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 |  |  |  |
Preferred stock, shares outstanding | 0 |  |  |  |  |  |  | 0 |  |  | 0 |  |  | 579 |
Stock option exercises, Shares |  |  |  |  |  |  |  | 0 |  | 0 | 0 | 0 |  |  |
Restricted stock unit settlements |  |  |  |  |  |  |  | 133 |  | 0 | 133 | 0 |  |  |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restricted stock unit settlements |  |  |  |  |  |  |  |  | 83 |  |  |  |  |  |
Direct Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock |  |  | $ 5,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Gross proceeds from issuance of common stock |  |  | 5,600,000 |  |  |  |  |  |  |  |  |  |  |  |
Placement agent fees and offering expenses |  |  | $ 600,000 |  |  |  |  |  |  |  |  |  |  |  |
Direct Offering [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued |  |  | 1,789,258 |  |  |  |  |  |  |  |  |  |  |  |
Common stock, price |  |  | $ 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 |  |  |  |  |  |  |  |  |  |  |  |
Series A Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares converted | 9,158 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding | 0 |  |  |  |  |  |  | 0 |  |  | 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 |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 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] | Series A Convertible Preferred Stock [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] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock value right to sell, maximum |  |  |  |  |  |  | $ 11,000,000 |  |  |  |  |  |  |  |
Common stock, par value |  |  |  |  |  |  | $ 0.001 |  |  |  |  |  |  |  |
Minimum percentage of common stock shares outstanding authorized to sell |  |  |  |  |  | 20.00% |  |  |  |  |  |  |  |  |
Common stock, shares issued |  |  |  |  |  |  | 12,352 |  |  |  |  |  |  |  |
Proceeds from issuance of common stock |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |
Common stock, shares issued |  |  |  |  |  |  |  | 124,000 |  |  | 124,000 |  |  |  |
Gross proceeds |  |  |  |  |  |  |  | $ 400,000 |  |  | $ 400,000 |  |  |  |
Common stock remaining available for sale under offering | $ 6,900,000 |  |  |  |  |  |  | 6,900,000 |  |  | $ 6,900,000 |  |  |  |
LPC [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Initial purchase of common stock |  |  |  |  |  |  |  |  |  |  |  |  | 32,895 |  |
Common stock, shares issued |  |  |  |  |  |  |  |  |  |  |  |  | 307,378 |  |
Gross proceeds |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,100,000 |  |
Offering expenses |  |  |  |  |  |  |  |  |  |  |  |  | $ 500,000 |  |
LPC [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, purchase price |  |  |  |  |  |  | $ 20.00 |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  | 8,000 |  |  |  |  |  |  |  |
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 is 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 |  |  |  |  |  |  |  |
Ladenburg Thalmann & Co. Inc [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period granted for underwriting option |  |  |  |  | 45 days |  |  |  |  |  |  |  |  |  |
Ladenburg Thalmann & Co. Inc [Member] | 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 |  |  |  |  |  |  |  |  |  |
H.C. Wainwright [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, par value |  | $ 0.001 |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock remaining available for sale under offering | $ 6,000,000 |  |  |  |  |  |  | $ 6,000,000 |  |  | $ 6,000,000 |  |  |  |
Percentage of commission on gross proceeds from sale of common stock |  | 3.00% |  |  |  |  |  |  |  |  |  |  |  |  |
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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