CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016	Jul. 01, 2016
Property, plant and equipment, accumulated depreciation	$ 132,188	$ 123,921	$ 124,227
Class A
Common stock, shares issued (shares)	8,783,099	8,778,028	8,816,675
Common stock, shares outstanding (shares)	8,783,099	8,778,028	8,816,675
Treasury stock, shares (shares)	67,137	64,323	33,561
Class B
Common stock, shares issued (shares)	1,211,686	1,212,006	1,212,344
Common stock, shares outstanding (shares)	1,211,686	1,212,006	1,212,344

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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