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Shareholders' Equity - Additional Information (Detail) | 12 Months Ended
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Sep. 30, 2014
Common Stock [Member] |
Class of Stock [Line Items] |
Right of holders to elect company's board of directors | 25.00%
Class B Stock [Member] |
Class of Stock [Line Items] |
Right of holders to elect company's board of directors | 75.00%

X
- Definition Right of holders to elect company's board of directors. + References No definition available. + Details
Name: | genc_RightOfHoldersToElectCompanysBoardOfDirectors
Namespace Prefix: | genc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_ClassOfStockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration