Computation of Basic and Diluted (Loss) Earnings per Share under Two-Class Method (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator for basic and diluted (loss) earnings per share:
Net (loss) income	$ (13,898)	$ 13,744	$ (59,504)	$ 55,189
Effect of reallocating undistributed earnings of participating securities		(90)		(379)
Net (loss) income available under the two-class method	$ (13,898)	$ 13,654	$ (59,504)	$ 54,810
Denominator:
Denominator for basic (loss) earnings per share- weighted-average shares	23,008,922	22,944,840	22,994,445	22,946,956
Effect of dilutive potential common shares	0	0	0	0
Denominator for diluted (loss) earnings per share- adjusted weighted-average shares	23,008,922	22,944,840	22,994,445	22,946,956
Basic (loss) earnings per share	$ (0.60)	$ 0.60	$ (2.59)	$ 2.39
Diluted (loss) earnings per share	$ (0.60)	$ 0.60	$ (2.59)	$ 2.39