Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income (loss)	$ 8,418,000	$ 7,043,000	$ (1,819,000)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Purchase of marketable securities	(492,674,000)	(550,295,000)	(384,668,000)
Proceeds from sale and maturity of marketable securities	491,852,000	549,027,000	383,773,000
Change in value of marketable securities	(1,126,000)	(314,000)	3,649,000
Deferred and other income taxes	1,285,000	1,647,000	(2,024,000)
Depreciation and amortization	1,128,000	1,397,000	1,385,000
Provision for doubtful accounts	115,000	105,000	60,000
Loss on disposal of assets	7,000	65,000	1,000
Stock-based compensation	71,000	37,000	253,000
Changes in assets and liabilities:
Accounts receivable	(189,000)	(341,000)	514,000
Costs and estimated earnings in excess of billings	(1,847,000)	(2,525,000)	(2,052,000)
Inventories	(5,053,000)	1,136,000	968,000
Prepaid expenses	(62,000)	(781,000)	32,000
Accounts payable	(123,000)	(86,000)	582,000
Customer deposits	4,144,000	66,000	4,094,000
Accrued expenses	162,000	812,000	(236,000)
Total adjustments	(2,310,000)	(50,000)	6,331,000
Cash flows provided by operating activities	6,108,000	6,993,000	4,512,000
Cash flows from investing activities:
Capital expenditures	(1,624,000)	(306,000)	(689,000)
Proceeds from sale of property and equipment	7,000
Cash flows used in investing activities	(1,617,000)	(306,000)	(689,000)
Cash flows from financing activities:
Proceeds from stock option exercises	223,000	380,000	136,000
Cash flows provided by financing activities	223,000	380,000	136,000
Net increase in cash	4,714,000	7,067,000	3,959,000
Cash and cash equivalents at:
Beginning of year	18,219,000	11,152,000	7,193,000
End of year	$ 22,933,000	$ 18,219,000	$ 11,152,000