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Product Warranty Liability (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Sep. 30, 2012
Product Warranty Liability [Abstract]
Income for product warranties	$ 3

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- Definition

Income for product warranties.

+ References

No definition available.

+ Details

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Namespace Prefix:	ghm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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- Details

Name:	us-gaap_ProductWarrantiesDisclosuresAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration