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Commitments and Contingencies - Additional Information (Detail) - USD ($) | 9 Months Ended | 34 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2015
December 7, 2012 Agreement [Member] |  |
Commitment And Contingencies [Line Items] |  |
Commitment towards investments in joint venture | $ 1,200,000 |
Contribution to joint venture |  | $ 850,000
December 9, 2014 Agreement [Member] |  |
Commitment And Contingencies [Line Items] |  |
Commitment towards investments in joint venture | $ 1,000,000 |

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