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Leases - Additional Information (Detail) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Dec. 31, 2022 USD ($) | Dec. 31, 2022 USD ($)
Leases [Line Items] |  |
Lessee, option to renew or terminate leases, description |  | Certain leases include options to renew or terminate. Renewal options are exercisable per the discretion of the Company and vary based on the nature of each lease.
Operating Lease Payments | $ 211 | $ 632
Remainder operating lease payment | 211 | 211
Future fixed minimum lease payments | $ 6,738 | $ 6,738
Minimum [Member] |  |
Leases [Line Items] |  |
Remaining term of contract |  | 1 year
Maximum [Member] |  |
Leases [Line Items] |  |
Remaining term of contract |  | 5 years

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- Definition Future fixed minimum lease payments. + References No definition available. + Details
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Balance Type: | credit
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- Definition Leases. + References No definition available. + Details
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Data Type: | xbrli:stringItemType
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- Definition Lessee operating and finance lease remaining term of contract. + References No definition available. + Details
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Namespace Prefix: | ghm_
Data Type: | xbrli:durationItemType
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- Definition Lessee operating lease and finance lease option to renew or terminate. + References No definition available. + Details
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- Definition Remainder Operating Lease Payment. + References No definition available. + Details
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Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 5 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=123391704&loc=SL77918643-209977 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (g)(1) -URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918686-209980 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
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- Details
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