Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows From Operating Activities:
Net income	$ 5,342,000	$ 1,218,000
Adjustments to reconcile net income to net cash provided (used in) by operating activities:
Stock-based compensation	91,000	122,000
Depreciation and amortization	182,000	127,000
Gain (loss) on marketable securities	59,000	(170,000)
Equity in income of unconsolidated affiliate	(87,000)	(277,000)
Operating lease expense, net of accretion	224,000	164,000
Changes in assets and liabilities:
Accounts receivable	(3,794,000)	(2,267,000)
Accounts receivable, related party	(192,000)	(454,000)
Inventories	155,000	(529,000)
Prepaid expenses	(650,000)	1,302,000
Accounts payable and accrued liabilities	1,072,000	(505,000)
Customer advance payments of orders	7,161,000
Lease liabilities	(221,000)	(160,000)
Net cash provided (used) by operating activities	9,342,000	(1,429,000)
Cash Flows From Investing Activities:
Purchase of property and equipment	(288,000)	(152,000)
Proceeds from sales of marketable securities	47,000	10,000
Net cash used in investing activities	(241,000)	(142,000)
Cash Flows From Financing Activities:
Proceeds from exercise of stock options	1,841,000	60,000
Repurchase of common stock	(125,000)	(1,008,000)
Net cash provided (used) by financing activities	1,716,000	(948,000)
Increase (decrease) in cash	10,817,000	(2,519,000)
Cash and cash equivalents, beginning of the period	6,548,000	7,007,000
Cash and cash equivalents, end of the period	$ 17,365,000	$ 4,488,000