Net Income (Loss) Per Share - Calculation of Basic and Diluted Weighted-Average Number of Shares of Common Stock and EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic:
Net income (loss), basic	$ 4,284	$ 3,998	$ 17,698	$ (17,662)
Net income (loss), shares, basic	35,684	20,144	32,343	19,947
Net income (loss), per share, basic	$ 0.12	$ 0.20	$ 0.55	$ (0.89)
Weighted-average number of shares of common stock-diluted:
Restricted stock and performance unit awards	13	26	127
Diluted:
Net income (loss), diluted	$ 4,284	$ 3,998	$ 17,698	$ (17,662)
Net income (loss), shares, diluted	35,697	20,170	32,471	19,947
Net income (loss), per share, diluted	$ 0.12	$ 0.20	$ 0.55	$ (0.89)