XML 39 R75.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Stock Compensation Plans - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock option awards granted |  |  | 49,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross |
Weighted average fair value of options granted |  |  | $ 4.97 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue |
Cash proceeds from the exercise of stock options | $ 47 us-gaap_ProceedsFromStockOptionsExercised | $ 581 us-gaap_ProceedsFromStockOptionsExercised | $ 83 us-gaap_ProceedsFromStockOptionsExercised |
Total intrinsic value of the stock options exercised | 32 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | 1,221 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | 203 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue |
Unrecognized stock-based compensation expense | 1,055 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized |  |  |
Weighted average period for recognize expense | 1 year 5 months 9 days |  |  |
Options, stock awards and performance awards available for future grants | 403,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant |  |  |
Stock Compensation Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock based compensation expense | 598 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember | 582 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember | 524 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember |
Income tax benefit to stock based compensation | 210 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember | 205 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember | 184 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember |
Increase in capital in excess of par value for the income tax benefit realized upon exercise of stock options and vesting of restricted | 197 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember | 268 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember | 41 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember |
Restricted Stock [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Restricted stock awarded | 30,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | 32,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | 26,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
Employee Stock Option [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Stock options maximum term |  |  | 10 years |
Stock option awards granted |  |  | 49,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Share-based compensation vesting percentage |  |  | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Vesting period |  |  | 3 years |
Amended and Restated 2000 Incentive Plan [Member] | Stock Compensation Plan [Member] | Maximum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of shares authorized | 1,375,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_AwardTypeAxis = us-gaap_StockCompensationPlanMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |
Amended and Restated 2000 Incentive Plan [Member] | Restricted Stock [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Restricted stock awarded | 30,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember | 32,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember | 26,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember |
Amended and Restated 2000 Incentive Plan [Member] | Restricted Stock [Member] | Performance Vested Restricted Stock [Member] | Officer [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based compensation vesting percentage | 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember / us-gaap_VestingAxis = ghm_PerformanceVestedRestrictedStockMember | 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember / us-gaap_VestingAxis = ghm_PerformanceVestedRestrictedStockMember |  |
Vesting period | 3 years | 3 years |  |
Restricted stock awarded | 12,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember / us-gaap_VestingAxis = ghm_PerformanceVestedRestrictedStockMember | 14,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember / us-gaap_VestingAxis = ghm_PerformanceVestedRestrictedStockMember | 18,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_OfficerMember / us-gaap_VestingAxis = ghm_PerformanceVestedRestrictedStockMember |
Amended and Restated 2000 Incentive Plan [Member] | Restricted Stock [Member] | Time Vested Restricted Stock [Member] | Officers and Key Employees [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based compensation vesting percentage | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = ghm_OfficersAndKeyEmployeesMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = ghm_OfficersAndKeyEmployeesMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember |  |
Vesting period | 3 years | 3 years |  |
Restricted stock awarded | 11,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = ghm_OfficersAndKeyEmployeesMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember | 12,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = ghm_OfficersAndKeyEmployeesMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember |  |
Amended and Restated 2000 Incentive Plan [Member] | Restricted Stock [Member] | Time Vested Restricted Stock [Member] | Director [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based compensation vesting percentage | 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember | 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember |  |
Vesting period | 1 year | 1 year |  |
Restricted stock awarded | 7,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember | 6,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember | 8,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember / us-gaap_VestingAxis = ghm_TimeVestedRestrictedStockMember |
Amended and Restated 2000 Incentive Plan [Member] | Restricted Stock [Member] | Maximum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of shares authorized | 250,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = ghm_AmendedAndRestated2000IncentivePlanMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |
Long Term Incentive Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Amounts paid to participant | 157 us-gaap_DeferredCompensationArrangementWithIndividualDistributionsPaid / us-gaap_PlanNameAxis = ghm_LongTermIncentivePlanMember |  |  |
Long Term Incentive Plan [Member] | Director [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Related liability recorded under plan | 158 us-gaap_DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent / us-gaap_PlanNameAxis = ghm_LongTermIncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember | 315 us-gaap_DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent / us-gaap_PlanNameAxis = ghm_LongTermIncentivePlanMember / us-gaap_TitleOfIndividualAxis = us-gaap_DirectorMember |  |
Long Term Incentive Plan [Member] | Subsequent Event [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Amounts paid to participant |  |  |  | 158 us-gaap_DeferredCompensationArrangementWithIndividualDistributionsPaid / us-gaap_PlanNameAxis = ghm_LongTermIncentivePlanMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Employee Stock Purchase Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of shares authorized | 200,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember |  |  |
Stock based compensation expense | 55 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | 57 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | 52 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember |
Income tax benefit to stock based compensation | 19 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | 20 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | 19 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember |
Increase in capital in excess of par value for the income tax benefit realized upon exercise of stock options and vesting of restricted | $ 3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | $ 3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | $ 2 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember |
Discounted purchase price of common stock percentage on fair market value | 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember |  |  |
Issue of treasury stock to the ESPP for the offering periods | 12,000 ghm_SharesPurchasedByEmployeeStockPurchasePlan / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | 16,000 ghm_SharesPurchasedByEmployeeStockPurchasePlan / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember | 19,000 ghm_SharesPurchasedByEmployeeStockPurchasePlan / us-gaap_PlanNameAxis = ghm_EmployeeStockPurchasePlanMember |

X
- Definition The number of shares purchased during the period by the Employee Stock Purchase Plan. + References No definition available. + Details
Name: | ghm_SharesPurchasedByEmployeeStockPurchasePlan
Namespace Prefix: | ghm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
Name: | us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of distributions made to the individual during the period. + References No definition available. + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualDistributionsPaid
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements. + References No definition available. + Details
Name: | us-gaap_DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 20 -Section 55 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=32706628&loc=d3e11374-113907 + Details
Name: | us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromStockOptionsExercised
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of vesting of share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Purchase price of common stock expressed as a percentage of its fair value. + References No definition available. + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_StockCompensationPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=ghm_AmendedAndRestated2000IncentivePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=ghm_EmployeeStockPurchasePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=ghm_LongTermIncentivePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |