v3.25.4

Revenue Recognition - Schedule of Disaggregation of Revenue (Detail) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2025 | Dec. 31, 2024
Disaggregation of Revenue [Abstract] |  |  |  |
Percentage of revenue from contracts recognized over time | 79.00% | 75.00% | 81.00% | 79.00%
Percentage of revenue from contracts recognized upon shipment | 21.00% | 25.00% | 19.00% | 21.00%

X
- Definition The percentage of total revenue from contracts from customers from the satisfaction of performance obligations at a point in time. + References No definition available. + Details
Name: | ghm_PercentageOfRevenueFromContractsWithCustomersExcludingAssessedTaxPerformanceObligationSatisfiedAtPointInTime
Namespace Prefix: | ghm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage of total revenue from contracts from customers from the satisfaction of performance obligations satisfied over time. + References No definition available. + Details
Name: | ghm_PercentageOfRevenueFromContractsWithCustomersExcludingAssessedTaxPerformanceObligationSatisfiedOverTime
Namespace Prefix: | ghm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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