Computation of Basic and Diluted Loss per Share under Two-Class Method (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator for basic and diluted loss per share:
Net loss	$ (19,950)	$ (13,898)	$ (64,930)	$ (59,504)
Effect of reallocating undistributed earnings of participating securities	0	0	0	0
Net loss available under the two-class method	$ (19,950)	$ (13,898)	$ (64,930)	$ (59,504)
Denominator:
Denominator for basic loss per share--weighted-average shares	24,770,252	23,008,922	23,651,332	22,994,445
Effect of dilutive potential common shares	0	0	0	0
Denominator for diluted loss per share--adjusted weighted-average shares	24,770,252	23,008,922	23,651,332	22,994,445
Basic loss per share	$ (0.81)	$ (0.60)	$ (2.75)	$ (2.59)
Diluted loss per share	$ (0.81)	$ (0.60)	$ (2.75)	$ (2.59)