Common shares - Additional Information (Detail) - $ / shares |
12 Months Ended | |||
|---|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Apr. 30, 2014 |
Nov. 30, 2013 |
|
| Common shares [Abstract] | ||||
| Common stock, shares authorized | 1,000,000,000 | 1,000,000,000 | ||
| Common stock, par value | $ 0.00025 | $ 0.00025 | $ 0.00025 | $ 0.00025 |
| Common stock, shares outstanding | 339,319,115 | 327,611,487 | ||
| Common stock voting rights, description | Each common share is entitled to one vote. The holders of common shares are also entitled to receive dividends whenever funds are legally available and when declared by the Board of Directors, which is subject to the approval by the holders of the common shares representing a majority of the aggregate voting power of all outstanding shares
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