XML 64 R52.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Income Taxes - Additional Information (Detail) - USD ($) | 9 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Mar. 31, 2021
Income Taxes [Line Items] |  |
Liability unrecognized tax benefits | $ 0 | $ 0
Earliest Tax Year [Member] | Federal Tax Jurisdictions [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2017 |
Earliest Tax Year [Member] | State Tax Jurisdictions [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2016 |
Earliest Tax Year [Member] | International Tax Jurisdictions [Member] | State Administration of Taxation, China [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2017 |
Earliest Tax Year [Member] | International Tax Jurisdictions [Member] | Ministry of Finance, India [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2019 |
Latest Tax Year [Member] | Federal Tax Jurisdictions [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2020 |
Latest Tax Year [Member] | State Tax Jurisdictions [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2020 |
Latest Tax Year [Member] | International Tax Jurisdictions [Member] | State Administration of Taxation, China [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2020 |
Latest Tax Year [Member] | International Tax Jurisdictions [Member] | Ministry of Finance, India [Member] |  |
Income Taxes [Line Items] |  |
Open tax year | 2020 |

X
- Definition Income taxes. + References No definition available. + Details
Name: | ghm_IncomeTaxesLineItems
Namespace Prefix: | ghm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax year that remains open to examination under enacted tax laws, in YYYY format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32718-109319 + Details
Name: | us-gaap_OpenTaxYear
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:gYearListItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 10B -URI http://asc.fasb.org/extlink&oid=123427490&loc=SL37586934-109318 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121826272&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_TaxPeriodAxis=us-gaap_EarliestTaxYearMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_DomesticCountryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_StateAdministrationOfTaxationChinaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_MinistryOfFinanceIndiaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TaxPeriodAxis=us-gaap_LatestTaxYearMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |