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Common Stock and Warrants - Warrants Outstanding and Exercisable (Detail) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 $ / shares shares | Mar. 31, 2018 $ / shares shares
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 1,798,941 | 1,798,941
Warrants Expiration Date, April 30, 2018 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 90,406 | 90,406
Exercise Price | $ / shares | $ 15.00 |
Expiration Date | Apr. 30, 2018 |
Warrants Expiration Date, June 26, 2018 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 33,546 | 33,546
Exercise Price | $ / shares | $ 15.00 |
Expiration Date | Jun. 26, 2018 |
Warrants Expiration Date, June 26, 2020 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 3,795 | 3,795
Exercise Price | $ / shares | $ 10.75 |
Expiration Date | Jun. 26, 2020 |
Warrants Expiration Date, July 17, 2018 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 12,576 | 12,576
Exercise Price | $ / shares | $ 15.00 |
Expiration Date | Jul. 17, 2018 |
Warrants Expiration Date, July 17, 2020 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 1,509 | 1,509
Exercise Price | $ / shares | $ 10.75 |
Expiration Date | Jul. 17, 2020 |
Warrants Expiration Date, April 18, 2019 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 961,489 | 961,489
Exercise Price | $ / shares |  | $ 7.50
Expiration Date | Apr. 18, 2019 |
Warrants Expiration Date, April 18, 2018 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 49,604 | 49,604
Exercise Price | $ / shares |  | $ 5.00
Expiration Date | Apr. 18, 2018 |
Warrants Expiration Date, December 22, 2020 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 270,915 | 270,915
Exercise Price | $ / shares | $ 12.25 |
Expiration Date | Dec. 22, 2020 |
Warrants Expiration Date, December 28, 2020 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 171,020 | 171,020
Exercise Price | $ / shares | $ 12.25 |
Expiration Date | Dec. 28, 2020 |
Warrants Expiration Date, December 29, 2020 |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants Outstanding | 204,081 | 204,081
Exercise Price | $ / shares | $ 12.25 |
Expiration Date | Dec. 29, 2020 |

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- Definition Expiration date of warrants held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column A + Details
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