Computation of Basic and Diluted (Loss) Earnings per Share under Two-Class Method (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator for basic and diluted (loss) earnings per share:
Net (loss) income	$ (15,197)	$ (19,950)	$ (20,296)	$ (24,684)	$ (50,040)	$ (13,898)	$ (17,004)	$ (28,602)	$ (80,127)	$ (109,544)	$ 55,588
Effect of reallocating undistributed earnings of participating securities											(376)
Net (loss) income available under the two-class method									$ (80,127)	$ (109,544)	$ 55,212
Denominator:
Denominator for basic (loss) earnings per share—weighted-average shares									24,377,839	22,999,318	22,946,395
Effect of dilutive potential common shares									0	0	0
Denominator for diluted (loss) earnings per share—adjusted weighted-average shares									24,377,839	22,999,318	22,946,395
Basic (loss) earnings per share	$ (0.57)	$ (0.81)	$ (0.88)	$ (1.07)	$ (2.17)	$ (0.60)	$ (0.74)	$ (1.24)	$ (3.29)	$ (4.76)	$ 2.41
Diluted (loss) earnings per share	$ (0.57)	$ (0.81)	$ (0.88)	$ (1.07)	$ (2.17)	$ (0.60)	$ (0.74)	$ (1.24)	$ (3.29)	$ (4.76)	$ 2.41