Balance Sheet Information - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Allowance for doubtful accounts	$ 86		$ 63
Consigned inventory with customers	400		900
Allowance for inventory losses	3,300		$ 3,300
Depreciation and amortization	$ 700	$ 700
Equipment [Member]
Property, Plant and Equipment [Line Items]
Period over which assets are depreciated	5 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Period over which assets are depreciated	7 years
Building [Member]
Property, Plant and Equipment [Line Items]
Period over which assets are depreciated	30 years
Minimum [Member]
Property, Plant and Equipment [Line Items]
Standard term of accounts receivable	30 days
Minimum [Member] | Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Period over which assets are depreciated	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Standard term of accounts receivable	90 days
Useful lives of the assets	1 year
Maximum [Member] | Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Period over which assets are depreciated	5 years