Earnings and Dividends per Share - Number of Shares Outstanding for Calculation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Basic net (loss) income and (loss) earnings per share, Numerator (Loss) Income	$ (901)	$ 5,486	$ 4,862	$ 5,524
Diluted (loss) earnings and (loss) earnings per share, Numerator (Loss) Income	$ (901)	$ 5,486	$ 4,862	$ 5,524
Basic net (loss) income and (loss) earnings per share, Denomiator (Shares)	34,669,810	34,473,688	34,631,519	34,345,317
Common stock equivalents arising from stock options, restricted stock awards, and employee stock purchase plan, Denominator (Shares)		333,000	83,000	341,000
Diluted (loss) earnings and (loss) earnings per share, Denominator (Shares)	34,669,810	34,806,808	34,715,141	34,685,687
Basic net (loss) income and (loss) earnings per share, Per Share Amount	$ (0.03)	$ 0.16	$ 0.14	$ 0.16
Diluted (loss) earnings and (loss) earnings per share, Per Share Amount	$ (0.03)	$ 0.16	$ 0.14	$ 0.16