Organization and Summary of Significant Accounting Policies - Net Sales by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Percentage of net sales by geographic area									100.00%	100.00%	100.00%
Net sales	$ 114,791	$ 104,836	$ 99,226	$ 101,215	$ 94,651	$ 90,262	$ 79,643	$ 79,242	$ 420,068	$ 343,798	$ 268,245
United States
Segment Reporting Information [Line Items]
Percentage of net sales by geographic area									79.80%	82.30%	81.60%
Net sales									$ 335,310	$ 282,810	$ 218,757
Other Countries
Segment Reporting Information [Line Items]
Percentage of net sales by geographic area									20.20%	17.70%	18.40%
Net sales									$ 84,758	$ 60,988	$ 49,488