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Stock-Based Compensation - Additional Information (Detail) |  |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 26, 2016 USD ($) shares | Jan. 19, 2016 USD ($) shares | Sep. 30, 2017 USD ($) shares | Sep. 30, 2016 shares | Sep. 30, 2015 shares | Sep. 30, 2014 shares | Mar. 17, 2009 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Common stock options issued to employees |  |  | 365,000 |  |  |  |
Stock split ratio |  |  | 1.5 |  |  |  |
2009 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Common stock options issued to employees |  |  | 0 | 75,000 |  |  |
Remaining contractual life on the options outstanding |  |  | 4 years 3 months 19 days |  |  |  |
Number of options, forfeited or cancelled |  |  | 0 |  |  |  |
Shares outstanding |  |  | 440,000 | 483,750 | 446,625 | 474,750 |
1997 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Shares available for granting |  |  | 0 |  |  |  |
Shares outstanding |  |  | 0 |  | 41,250 | 41,250 |
January 19, 2016 Class B Stock Options [Member] | 2009 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Common stock options issued to employees |  | 30,000 | 45,000 |  |  |  |
Options vesting rate |  | 25.00% |  |  |  |  |
Options vesting period |  |  | Options vest at 25% per year starting on January 19, 2017 and each year thereafter through January 19, 2020 |  |  |  |
Options exercisable |  |  | Oct. 01, 2021 |  |  |  |
Estimated fair value of options at time of grant | $ |  | $ 138,000 |  |  |  |  |
Compensation expense remaining to be expensed | $ |  |  | $ 78,000 |  |  |  |
September 26, 2016 Class B Stock Options [Member] | 2009 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Common stock options issued to employees | 30,000 |  |  |  |  |  |
Options vesting rate | 25.00% |  |  |  |  |  |
Options vesting period |  |  | Options vest at 25% per year starting on September 26, 2017 and each year thereafter through September 26, 2020 |  |  |  |
Options exercisable |  |  | Sep. 26, 2026 |  |  |  |
Estimated fair value of options at time of grant | $ | $ 147,000 |  |  |  |  |  |
Compensation expense remaining to be expensed | $ |  |  | $ 110,000 |  |  |  |
Common Stock [Member] | 2009 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Maximum number of shares granting of awards |  |  |  |  |  |  | 800,000
Shares available for granting |  |  | 482,000 |  |  |  |
Common Stock [Member] | 1997 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Incentive and nonqualified stock options, Number of shares authorized to purchase |  |  | 1,200,000 |  |  |  |
Percentage of common stock to be purchased of authorized common stock of any subsidiary |  |  | 15.00% |  |  |  |
Options expiration period after date of grant |  |  | 10 years |  |  |  |
Class B Stock [Member] | 2009 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Maximum number of shares granting of awards |  |  |  |  |  |  | 160,000
Shares available for granting |  |  | 100,000 |  |  |  |
Class B Stock [Member] | 1997 Plan [Member] |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |
Incentive and nonqualified stock options, Number of shares authorized to purchase |  |  | 1,200,000 |  |  |  |

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- Definition Description of the period in which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition. + References No definition available. + Details
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- Definition Fair value of options granted. + References No definition available. + Details
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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Date the equity-based award expires, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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