Organization, Basis of Presentation and Summary of Significant Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Basis Of Presentation [Line Items]
Common Stock, par value	$ 0.001		$ 0.001
Preferred Stock, par value	$ 0.001
Inventory obsolescence reserved	$ 336	$ 200	$ 187
Sales return maximum duration	18 months
Offered period for sales return prior to expiration	6 months
Offered period for sales return subsequent to expiration	12 months
Discount for prompt payment	2.00%
Research and development expense		$ 2,484
Future minimum lease payments	$ 1,200
Right of use lease asset	887
Right of use lease liability	$ 1,006
Minimum [Member]
Basis Of Presentation [Line Items]
Accrual to payment cycle period	1 month
Maximum [Member]
Basis Of Presentation [Line Items]
Accrual to payment cycle period	3 months