Computation of Basic and Diluted Loss per Share under Two-Class Method (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Numerator for basic and diluted loss per share:
Net loss	$ (19,994)	$ (22,272)
Effect of reallocating undistributed earnings of participating securities	0	0
Net loss available under the two-class method	$ (19,994)	$ (22,272)
Denominator:
Denominator for basic loss per share--weighted-average shares	27,464,717	26,788,591
Effect of dilutive potential common shares	0	0
Denominator for diluted loss per share--adjusted weighted-average shares	27,464,717	26,788,591
Basic loss per share	$ (0.73)	$ (0.83)
Diluted loss per share	$ (0.73)	$ (0.83)

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 portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount of undistributed earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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