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Accrued Expenses - Additional Information (Detail) (USD $)	12 Months Ended
	Sep. 30, 2013
Payables And Accruals [Abstract]
Reduction in estimated advertising expenses for the 2014 ConExpo show	$ 750,000

X

- Definition

Estimated reduction in advertising expenses in next year.

+ References

No definition available.

+ Details

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Namespace Prefix:	genc_
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Balance Type:	credit
Period Type:	duration

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- Details

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Namespace Prefix:	us-gaap_
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