Income Taxes - Tax Effects of Temporary Differences and Carryforwards (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Deferred Tax Assets [Abstract]
Inventory reserve	$ 345,000	$ 286,000
Other reserves and accruals	262,000	338,000
Stock-based compensation	2,000	8,000
Tax credit carryforwards	318,000	1,717,000
Federal tax loss carryforwards		892,000
State tax loss carryforwards	23,000	252,000
Foreign tax loss carryforwards	34,000	35,000
Total deferred income taxes	984,000	3,528,000
Valuation allowance		(379,000)
Total deferred income tax liabilities	1,074,000	97,000
Net deferred tax (liabilities) assets	(90,000)
Net deferred tax (liabilities) assets		3,052,000
Deferred Tax Liabilities [Abstract]
Fixed assets	44,000	58,000
Unrealized gains on marketable securities	1,024,000	27,000
Other	6,000	12,000
Total deferred income tax liabilities	$ 1,074,000	$ 97,000