Condensed Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Sep. 30, 2017
Current assets:
Cash and cash equivalents	$ 24,863,000	$ 22,933,000
Marketable securities at fair value (cost $87,605,000 at December 31, 2017 and $86,967,000 at September 30, 2017)	88,340,000	87,886,000
Accounts receivable, less allowance for doubtful accounts of $240,000 at December 31, 2017 and $207,000 at September 30, 2017	1,317,000	1,184,000
Costs and estimated earnings in excess of billings	5,727,000	6,768,000
Inventories, net	16,925,000	16,687,000
Prepaid expenses & other current assets	1,250,000	1,660,000
Total Current Assets	138,422,000	137,118,000
Property and equipment, net of accumulated depreciation	7,376,000	5,722,000
Other assets	53,000	53,000
Total Assets	145,851,000	142,893,000
Current Liabilities:
Accounts payable	3,315,000	1,320,000
Customer deposits	7,313,000	8,628,000
Accrued expenses	2,799,000	2,426,000
Total Current Liabilities	13,427,000	12,374,000
Deferred and other income taxes	875,000	1,601,000
Total Liabilities	14,302,000	13,975,000
Commitments and contingencies
Shareholders' equity:
Preferred stock, par value $.10 per share; authorized 300,000 shares; none issued
Capital in excess of par value	11,457,000	11,178,000
Retained earnings	118,645,000	116,299,000
Total Shareholders' Equity	131,549,000	128,918,000
Total Liabilities and Shareholders' Equity	145,851,000	142,893,000
Common Stock [Member]
Shareholders' equity:
Common stock	1,218,000	1,215,000
Class B Stock [Member]
Shareholders' equity:
Common stock	$ 229,000	$ 226,000

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.