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Common Stock and Warrants - Summary of Warrant Activity (Detail) | 3 Months Ended
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Mar. 31, 2018 $ / shares shares | Mar. 31, 2018 $ / shares shares
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants, Outstanding, ending balance | 1,798,941 | 1,798,941
CAD |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants, Outstanding, beginning balance | 1,011,505 | 1,011,505
Number of Warrants, Granted | 206 | 206
Number of Warrants, Exercised | (618) | (618)
Number of Warrants, Outstanding, ending balance | 1,011,093 | 1,011,093
Weighted-Average Exercise Price, Outstanding, beginning balance | $ / shares |  | $ 7.38
Weighted-Average Exercise Price, Granted | $ / shares |  | 7.50
Weighted-Average Exercise Price, Exercised | $ / shares |  | 5.83
Weighted-Average Exercise Price, Outstanding, ending balance | $ / shares |  | $ 7.38
USD |  |
Class Of Warrant Or Right [Line Items] |  |
Number of Warrants, Outstanding, beginning balance | 1,343,404 | 1,343,404
Number of Warrants, Exercised | (555,556) | (555,556)
Number of Warrants, Outstanding, ending balance | 787,848 | 787,848
Weighted-Average Exercise Price, Outstanding, beginning balance | $ / shares | $ 10.25 |
Weighted-Average Exercise Price, Exercised | $ / shares | 6.75 |
Weighted-Average Exercise Price, Outstanding, ending balance | $ / shares | $ 12.72 |

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- Definition Exercise price per share or per unit of warrants or rights outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(i)(4)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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