Private Equity Securities Offerings (Detail) - USD ($)
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1 Months Ended |
12 Months Ended |
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Apr. 02, 2021 |
Mar. 18, 2021 |
Jan. 28, 2021 |
Dec. 08, 2020 |
Dec. 06, 2020 |
Dec. 04, 2020 |
Nov. 30, 2020 |
Nov. 17, 2020 |
Oct. 26, 2020 |
Oct. 14, 2020 |
Jun. 17, 2020 |
Mar. 13, 2020 |
Mar. 04, 2020 |
Feb. 28, 2020 |
Jan. 31, 2020 |
Dec. 30, 2019 |
Dec. 20, 2019 |
Aug. 29, 2019 |
Jul. 31, 2019 |
Mar. 20, 2019 |
Jan. 31, 2020 |
Nov. 08, 2019 |
May 31, 2021 |
May 31, 2020 |
May 31, 2019 |
Jan. 28, 2020 |
Nov. 30, 2019 |
Oct. 11, 2019 |
Oct. 10, 2019 |
Aug. 31, 2019 |
Class of Stock [Line Items] |
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Stock price, in dollars per share |
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$ 1.50
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$ 0.50
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Exercise price of warrants, per share |
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$ 1.00
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$ 0.50
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Common stock warrants to purchase shares |
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300,000
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2,600,000
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Term of warrants |
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5 years
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5 years
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Preferred Stock Shares authorized to be issued |
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5,000,000
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5,000,000
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Common stock, par value |
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$ 0.001
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$ 0.001
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$ 0.001
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$ 0.001
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$ 0.001
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Preferred stock, par value |
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$ 0.001
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$ 0.001
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Stock issued via offering, tender or placement, value |
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$ 13,409,000
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$ 3,084,000
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Shares issued on debt conversion |
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19,900,000
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Maximum |
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Class of Stock [Line Items] |
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Exercise price of warrants, per share |
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$ 1.35
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Minimum |
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Class of Stock [Line Items] |
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Exercise price of warrants, per share |
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$ 0.30
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Private Placement [Member] |
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Class of Stock [Line Items] |
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Stock price, in dollars per share |
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$ 1.50
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$ 0.50
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Exercise price of warrants, per share |
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$ 0.75
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Warrant covering common stock shares purchased, percentage |
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50.00%
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Shares issued during the period new issues shares |
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670,000
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47,000,000.0
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Common stock warrants to purchase shares |
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23,500,000
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Term of warrants |
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5 years
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Stock issued via offering, tender or placement, value |
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$ 1,000,000
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$ 23,488,000
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Proceeds from issuance of common stock |
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$ 1,000,000.0
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23,500,000
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Placement agent fees and expenses |
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2,700,000
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Accredited Investors [Member] |
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Class of Stock [Line Items] |
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Exercise price of warrants, per share |
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$ 0.50
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Common stock warrants to purchase shares |
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3,900,000
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Stock issued via offering, tender or placement, value |
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$ 3,200,000
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Certain Lead Investors [Member] |
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Class of Stock [Line Items] |
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Common stock warrants to purchase shares |
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1,000,000.0
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Private Warrant Exchange [Member] |
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Class of Stock [Line Items] |
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Stock price, in dollars per share |
$ 0.90
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$ 0.24
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0.36
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$ 0.60
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$ 0.45
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$ 0.50
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$ 0.40
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Exercise price of warrants, per share |
$ 0.45
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$ 0.30
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$ 0.45
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$ 0.75
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$ 0.75
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$ 0.50
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$ 0.50
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$ 0.50
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Shares issued during the period new issues shares |
1,100,000
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200,000
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3,600,000
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2,000,000.0
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300,000
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500,000
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5,000,000.0
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7,000,000.0
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16,500,000
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88,000
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8,600,000
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2,700,000
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4,700,000
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11,300,000
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4,400,000
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Common stock warrants to purchase shares |
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37,100,000
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Warrants exchanged (in shares) |
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2,500,000
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1,900,000
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300,000
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500,000
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4,500,000
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6,400,000
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16,500,000
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34,100,000
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Stock issued via offering, tender or placement, value |
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$ 17,556,000
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6,021,000
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$ 2,966,000
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Proceeds from issuance of common stock |
$ 700,000
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$ 100,000
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$ 2,900,000
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$ 400,000
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$ 100,000
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$ 300,000
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$ 1,600,000
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$ 2,700,000
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$ 7,400,000
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$ 36,000
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$ 2,200,000
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$ 1,100,000
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$ 800,000
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$ 3,000,000.0
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$ 1,900,000
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Placement agent fees and expenses |
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100,000
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400,000
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300,000
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Noncash inducement interest expense |
$ 100,000
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$ 32,000
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$ 3,400,000
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$ 700,000
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$ 100,000
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$ 200,000
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$ 1,400,000
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$ 2,200,000
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$ 3,300,000
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$ 200,000
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$ 11,400,000
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5,500,000
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Private Warrant Exchange [Member] | Maximum |
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Class of Stock [Line Items] |
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Stock price, in dollars per share |
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$ 0.90
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$ 0.75
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$ 0.60
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$ 0.80
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$ 0.70
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$ 0.45
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$ 0.25
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Exercise price of warrants, per share |
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0.45
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1.50
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0.75
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1.00
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1.35
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0.75
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0.75
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Private Warrant Exchange [Member] | Minimum |
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Class of Stock [Line Items] |
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Stock price, in dollars per share |
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0.60
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0.45
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0.24
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0.24
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0.21
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0.18
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0.22
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Exercise price of warrants, per share |
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$ 0.30
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$ 0.90
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$ 0.30
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$ 0.30
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$ 0.35
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$ 0.30
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$ 0.45
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Private Warrant Exchange, Non-Inducement Shares [Member] |
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Class of Stock [Line Items] |
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Shares issued during the period new issues shares |
800,000
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100,000
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80,000
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7,800,000
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2,200,000
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3,400,000
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7,500,000
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4,000,000.0
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Private Warrant Exchange, Inducement Shares [Member] |
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Class of Stock [Line Items] |
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Shares issued during the period new issues shares |
300,000
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100,000
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8,000
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800,000
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500,000
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1,300,000
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3,800,000
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400,000
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Allotment to placement agent |
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Class of Stock [Line Items] |
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Common stock warrants to purchase shares |
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4,400,000
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700,000
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Term of warrants |
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5 years
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Allotment to placement agent | Maximum |
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Class of Stock [Line Items] |
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Exercise price of warrants, per share |
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$ 0.44
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Allotment to placement agent | Minimum |
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Class of Stock [Line Items] |
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|
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|
|
|
|
|
|
|
|
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|
|
|
|
|
|
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|
Exercise price of warrants, per share |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
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|
$ 0.40
|
|
|
|
Public Warrant Tender Offering [Member] |
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|
|
|
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|
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|
|
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|
|
|
|
|
|
|
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|
|
|
|
|
|
|
Class of Stock [Line Items] |
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|
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|
|
|
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|
|
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|
|
|
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|
|
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|
|
|
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|
Stock issued via offering, tender or placement, value |
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
$ 11,900,000
|
|
|
|
|
|
|
Series B Convertible Preferred Stock |
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Class of Stock [Line Items] |
|
|
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|
|
|
|
|
|
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|
|
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|
|
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|
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|
Preferred Stock Shares authorized to be issued |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
400,000
|
400,000
|
|
|
|
|
|
|
Preferred stock, par value |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 0.001
|
$ 0.001
|
|
|
|
|
|
|
Series C Convertible Preferred Stock |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Class of Stock [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Stock price, in dollars per share |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 1,000.00
|
|
|
|
|
|
|
|
|
|
|
|
|
Shares issued during the period new issues shares |
|
|
|
|
415
|
|
|
|
|
|
|
|
|
|
|
|
|
1,754
|
|
|
|
2,788
|
|
|
|
|
|
|
|
|
Preferred Stock Shares authorized to be issued |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
8,203
|
8,000
|
|
8,203
|
|
20,000
|
5,000
|
|
Preferred stock, par value |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 0.001
|
$ 0.001
|
|
|
|
|
|
|
Stock issued via offering, tender or placement, value |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 1,500,000
|
|
|
|
|
|
|
|
|
|
|
|
|
Placement agent fees and expenses |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 200,000
|
|
|
|
|
|
|
|
|
|
|
|
|
Series C Convertible Preferred Stock | Accredited Investors [Member] |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Class of Stock [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Shares issued during the period new issues shares |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
3,246
|
|
|
|
|
|
|
|
|
|
|
Series D Convertible Preferred Stock |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Class of Stock [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Stock price, in dollars per share |
|
|
|
|
|
|
|
|
|
|
|
$ 1,000.00
|
|
|
$ 1,000.00
|
|
|
|
|
|
$ 1,000.00
|
|
|
|
|
|
|
|
|
|
Shares issued during the period new issues shares |
|
|
|
|
|
|
|
|
|
|
|
882
|
|
|
7,570
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Preferred Stock Shares authorized to be issued |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
11,737
|
12,000
|
|
|
|
|
|
|
Preferred stock, par value |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 0.001
|
|
|
|
|
|
$ 0.001
|
|
$ 0.001
|
$ 0.001
|
|
|
|
|
|
|
Stock issued via offering, tender or placement, value |
|
|
|
|
|
|
|
|
|
|
|
$ 900,000
|
|
|
$ 7,600,000
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Placement agent fees and expenses |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
$ 4,645
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|