Revenue Recognition - Schedule of Disaggregation of Revenue (Detail)	3 Months Ended	9 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Abstract]
Percentage of revenue from contracts recognized upon shipment	24.00%	20.00%	23.00%	27.00%
Percentage of revenue from contracts recognized over time	76.00%	80.00%	77.00%	73.00%

The percentage of total revenue from contracts from customers from the satisfaction of performance obligations at a point in time.

No definition available.

Name:	ghm_PercentageOfRevenueFromContractsWithCustomersExcludingAssessedTaxPerformanceObligationSatisfiedAtPointInTime
Namespace Prefix:	ghm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration