Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Nature Of Operations [Line Items]
Percentage of revenue transacted in foreign currency			3.00%	5.00%
Percentage of expenses transacted in foreign currency			17.00%	25.00%
Net foreign exchange gains (losses) resulting from foreign currency transactions included in other income			$ (300,000)	$ 100,000
Cash and cash equivalents maturities			90 days	90 days
Investment of cash equivalents are redeemable upon demand using amortized cost method			$ 1.00
Investment in money market funds restricted by investment in short term securities, percentage			100.00%
Short-term investments, maturities, minimum			90 days
Short-term investments, maturities, maximum			1 year
Long-term investments, maturities, minimum			1 year
Long-term investments, maturities, maximum			2 years
Net unrealized losses			$ 8,000	$ 10,000
Allowance for doubtful accounts			113,000	104,000
Recovery of amounts previously written off			177,000
Consigned inventory with customers			300,000	300,000
Allowance for inventory losses			3,700,000	3,400,000
Depreciation and amortization			3,000,000.0	2,900,000
Advertising expense			$ 200,000	200,000
Most likely than not benefit likelihood percentage being realized upon ultimate settlement with taxing authority resulting from sustainability of tax examination			50.00%
Deferred tax asset, valuation allowance			$ 12,938,000	13,490,000
Deferred payroll taxes			500,000
Impairment of long-lived assets			$ 0	0
Test & Measurement Product Line [Member]
Nature Of Operations [Line Items]
Goodwill impairment test			October 31, 2020
Goodwill acquired	$ 3,300,000
Test & Measurement Product Line [Member] | Product [Member]
Nature Of Operations [Line Items]
Goodwill impairment test			October 31, 2019
Goodwill acquired		$ 3,300,000
Equipment [Member]
Nature Of Operations [Line Items]
Period over which assets are depreciated			5 years
Furniture and Fixtures [Member]
Nature Of Operations [Line Items]
Period over which assets are depreciated			7 years
Building [Member]
Nature Of Operations [Line Items]
Period over which assets are depreciated			30 years
Level 3 [Member]
Nature Of Operations [Line Items]
Investments			$ 0	0
China [Member]
Nature Of Operations [Line Items]
Cash in foreign bank			2,900,000	$ 2,100,000
Maximum [Member]
Nature Of Operations [Line Items]
Federal Deposit Insurance Corporation insured limit			$ 250,000
Standard term of accounts receivable			90 days
Useful lives of the assets			1 year
Maximum [Member] | Computer Equipment [Member]
Nature Of Operations [Line Items]
Period over which assets are depreciated			5 years
Minimum [Member]
Nature Of Operations [Line Items]
Standard term of accounts receivable			30 days
Minimum [Member] | Computer Equipment [Member]
Nature Of Operations [Line Items]
Period over which assets are depreciated			3 years