Condensed Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operations:
Net income	$ 6,156,000	$ 10,217,000
Adjustments to reconcile net income to cash flows provided by operating activities:
Purchases of marketable securities	(112,668,000)	(152,063,000)
Proceeds from sale and maturity of marketable securities	110,805,000	152,678,000
Change in fair value of marketable securities	1,510,000	(1,324,000)
Deferred income taxes	(2,066,000)	(25,000)
Depreciation and amortization	1,244,000	1,188,000
Provision for doubtful accounts	50,000	100,000
Stock-based compensation	53,000	53,000
Changes in assets and liabilities:
Accounts receivable	(56,000)	(589,000)
Costs and estimated earnings in excess of billings	3,774,000	(8,622,000)
Inventories	804,000	(1,781,000)
Prepaid expenses and other current assets	(1,150,000)	959,000
Accounts payable	182,000	756,000
Customer deposits	733,000	(2,101,000)
Accrued expenses and other current liabilities	34,000	577,000
Total adjustments	3,249,000	(10,194,000)
Cash flows provided by operating activities	9,405,000	23,000
Cash flows used in investing activities:
Capital expenditures	(1,246,000)	(1,600,000)
Cash flows used in investing activities	(1,246,000)	(1,600,000)
Cash flows from financing activities:
Proceeds from stock option exercises	103,000
Cash flows provided by financing activities	103,000
Net increase (decrease) in cash	8,262,000	(1,577,000)
Cash at:
Beginning of period	10,302,000	8,012,000
End of period	$ 18,564,000	$ 6,435,000