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Stockholders' equity - Additional Information (Detail) (USD $) | 1 Months Ended | 12 Months Ended |  |  |  | 1 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Nov. 09, 2012 | May 17, 2012 | Dec. 31, 2013 | Dec. 31, 2012 | Aug. 05, 2009 | Nov. 09, 2012 Efftec International Inc | Nov. 09, 2012 Scott Macon Ltd | Jul. 07, 2010 Stock Unit | Mar. 07, 2011 2010 Offering | Mar. 04, 2011 2010 Offering | Jul. 07, 2010 2010 Offering | Aug. 05, 2009 2009 Offering | May 17, 2012 Common Stock [Member] | Dec. 31, 2012 Common Stock [Member] | Jul. 07, 2010 Common Stock [Member]
Stockholders Equity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, issued |  |  | 25,070,386 | 24,124,625 |  | 133,589 | 26,716 | 2,737,500 |  |  | 1,368,750 | 1,470,000 |  |  | 2,737,500
Common stock, par value |  |  | $ 0.01 | $ 0.01 | $ 1.4375 | $ 3.743 | $ 3.743 |  |  |  | $ 2.00 | $ 1.15 |  |  |
Net proceeds from issuance of common stock |  |  |  |  |  |  |  |  |  |  | $ 4,900,000 | $ 1,400,000 |  |  |
Stock issued during period, shares, issued for services |  |  |  |  |  |  |  |  |  |  |  | 73,500 | 20,000 | 20,000 |
Stock issued during period, value, issued for services |  | 74,000 |  | 74,000 |  |  |  |  |  |  |  |  |  | 0 |
Class of warrant or right, exercise price of warrants or rights |  |  |  |  |  |  |  |  |  | 0.60 | 2.60 |  |  |  |
Adjustment of warrants granted for services |  |  |  |  |  |  |  |  |  |  | 1,300,000 |  |  |  |
Estimated fair value of the warrant |  |  |  |  |  |  |  |  |  |  |  | 48,000 |  |  |
Class of warrant or right repurchase during period |  |  |  |  |  |  |  |  |  | 150,000 |  |  |  |  |
Class of warrant or right issued unit during period |  |  |  |  |  |  |  |  | 1,218,750 |  |  |  |  |  |
Class of warrants expiration date |  |  | Jul. 07, 2016 |  |  |  |  |  |  |  |  |  |  |  |
Fair value of shares issued for services | $ 100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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