Organization and Summary of Significant Accounting Policies - Weighted Average Number of Shares Outstanding and Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator for basic and diluted earnings per share:
Net income	$ (2,071)	$ 422	$ 2,276	$ 4,580	$ 6,341	$ 3,843	$ 3,650	$ 3,463	$ 5,207	$ 17,297	$ 19,933
Denominator:
Weighted average shares outstanding—basic (in shares)									52,726	52,667	53,548
Dilutive effect of stock-based awards (in shares)									1,172	869	1,090
Diluted weighted average shares outstanding (in shares)									53,898	53,536	54,638
Anti-dilutive stock-based awards excluded (in shares)									386	443	198
Net income per common share:
Basic (in dollars per share)	$ (0.04)	$ 0.01	$ 0.04	$ 0.09	$ 0.12	$ 0.07	$ 0.07	$ 0.06	$ 0.10	$ 0.33	$ 0.37
Diluted (in dollars per share)	$ (0.04)	$ 0.01	$ 0.04	$ 0.09	$ 0.12	$ 0.07	$ 0.07	$ 0.06	$ 0.10	$ 0.32	$ 0.36