Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 26, 2017	Oct. 22, 2014	Nov. 01, 2007
Equity [Abstract]
Stock repurchase program, authorized amount							$ 50,000,000
Stock repurchase program, additional authorized amount						$ 30,000,000
Repurchased shares	105,750	48,687		0
Repurchased shares, value	$ 729,000	$ 328,000	$ 729,000
Stock repurchase program, average cost	$ 6.90	$ 6.73
Stock repurchase program, remaining authorized repurchase amount		$ 33,400,000
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001
Series B Junior Participating Preferred Stock
Class of Stock [Line Items]
Right, exercise price (in dollars per share)					$ 30.00