XML 47 R31.htm IDEA: XBRL DOCUMENT
v3.20.2

Revenue Recognition - Schedule of Net Contract Assets (Liabilities) (Detail) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Sep. 30, 2020 | Mar. 31, 2020
Revenue From Contract With Customer [Abstract] |  |
Unbilled revenue (contract assets) | $ 13,691 | $ 14,592
Customer deposits (contract liabilities) | (24,838) | (26,983)
Net contract liabilities | (11,147) | $ (12,391)
Unbilled revenue (contract assets) | (901) |
Customer deposits (contract liabilities) | 2,145 |
Net contract liabilities | $ 1,244 |

X
- Definition The change in the balance of the contract with customer asset. + References No definition available. + Details
Name: | ghm_ChangeInContractWithCustomerAsset
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The change in the net balance of the contract with customer asset and contract with customer liability. + References No definition available. + Details
Name: | ghm_ChangeInContractWithCustomerAssetLiabilityNet
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The change in the balance of the contract with customer liability. + References No definition available. + Details
Name: | ghm_ChangeInContractWithCustomerLiability
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The net balance of current contract with customer assets and current contract with customer liabilities. + References No definition available. + Details
Name: | ghm_ContractWithCustomerNetAssetLiabilityCurrent
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130533-203044 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045 + Details
Name: | us-gaap_ContractWithCustomerAssetNetCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130532-203044 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045 + Details
Name: | us-gaap_ContractWithCustomerLiabilityCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration