Basic Net Income (loss) Per Share is Calculated Using Weighted Average Number of Shares (Detail) - $ / shares	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Earnings per share - basic	$ 1.01	$ 0.46
Earnings per share - diluted	$ 0.90	$ 0.41
Weighted average shares of common stock outstanding - basic	25,525,786	24,673,081
Weighted average shares of common stock outstanding - diluted	28,661,735	27,970,431

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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