XML 78 R65.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Employee Benefit Plans - Additional Information (Detail) shares in Thousands | 12 Months Ended
--- | ---
Mar. 31, 2016 USD ($) $ / Employee shares | Mar. 31, 2015 USD ($) shares | Mar. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |
Employee's years of service and average earnings | Five highest consecutive calendar years of compensation in the ten-year period preceding retirement |  |
Percentage of blue collar employees | 50.00% |  |
Increase in projected benefit obligations | $ 2,145,000 |  |
Accumulated benefit obligation | $ 32,270,000 | $ 33,998,000 |
Contribution equal to employee salary deferral | 100.00% |  |
Employer contribution description | Matching contributions equal to 100% of the first 3% of an employee’s salary deferral and 50% of the next 2% percent of an employee’s salary deferral |  |
Contribution next to employee salary deferral | 3.00% |  |
Contribution for additional employee salary deferral | 50.00% |  |
Contribution additional next to employee salary deferral | 2.00% |  |
Share of the medical premium cost for family coverage | $ 4,000 |  |
Share of the medical premium cost for single coverage | 2,000 |  |
Share of the medical premium both family and single coverage for regular retirees | $ 1,000 |  |
Medical care cost trend rate | 5.00% |  |
Medical care trend year | 2022 |  |
Medical care cost trend rate decrements | 0.50% |  |
Current portion of accrued postretirement benefit obligation | $ 88,000 | $ 92,000 |
Employee stock ownership plan, shares | shares | 202 | 233 |
Company contributions to the ESOP | $ 0 | $ 0 | $ 0
Stop loss coverage per employee for claims | $ / Employee | 100 |  |
Maximum aggregate stop loss coverage | $ / Employee | 1,000 |  |
Total plan amount | $ 2,602,000 |  |
Self-Insured medical plan liability | 176,000 | 446,000 |
Defined Contribution Plan 401K [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions to defined contribution plan | 866,000 | 940,000 | 831,000
Pension Plans, Defined Benefit [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Liability released through annuity purchase | (1,710,000) |  |
Annuities purchased | (1,798,000) |  |
Estimated net actuarial loss for pension plan | 1,351,000 |  |
Estimated prior service cost for pension plan | 0 |  |
Pension expense | $ (49,000) | $ (469,000) | $ 213,000
Weighted average discount rate used to develop net postretirement benefit cost | 3.74% | 4.46% | 4.28%
Defined Contribution Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions to defined contribution plan | $ 315,000 | $ 294,000 | $ 257,000
Supplemental Executive Retirement Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension expense | 76,000 | 70,000 | 70,000
Pension expense related liability | 391,000 | 341,000 |
Current portion of the related liability included in accrued compensation | 26,000 | 26,000 |
Other Postretirement Benefit Plans [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Estimated net actuarial loss for pension plan | 39,000 |  |
Estimated prior service cost for pension plan | 0 |  |
Pension expense | $ 69,000 | $ (40,000) | $ (87,000)
Weighted average discount rate used to develop net postretirement benefit cost | 3.11% | 3.59% | 3.26%

X
- Definition Current portion of the accrued postretirement liability recorded in the consolidated balance sheet. + References No definition available. + Details
Name: | ghm_AccruedPostretirementBenefitLiabilityCurrent
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Aggregate annual stop loss coverage amount per employee for claims incurred. + References No definition available. + Details
Name: | ghm_AggregateStopLossInsuranceCoveragePerEmployee
Namespace Prefix: | ghm_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate annual stop loss coverage for the entire medical plan. + References No definition available. + Details
Name: | ghm_AnnualPlanAggregateStopLossInsuranceCoverage
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Company's share of the medical premium cost for early retirees for family coverage under the other postretirement plan. + References No definition available. + Details
Name: | ghm_CompanyShareOfMedicalPremiumCostForEarlyRetireeFamilyCoverageUnderOtherPostretirementPlan
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Company's share of the medical premium cost for early retirees for single coverage under the other postretirement plan. + References No definition available. + Details
Name: | ghm_CompanyShareOfMedicalPremiumCostForEarlyRetireeSingleCoverageUnderOtherPostretirementPlan
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Company's share of the medical premium cost for regular retirees for coverage under the other postretirement plan. + References No definition available. + Details
Name: | ghm_CompanyShareOfMedicalPremiumCostForRegularRetireeCoverageUnderOtherPostretirementPlan
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The employer matching contribution percentage on the 2% employee salary deferral after the first 3% employee salary deferral. + References No definition available. + Details
Name: | ghm_DefinedAdditionalContributionPlanEmployerMatchingContributionPercent
Namespace Prefix: | ghm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Average earnings description for calculation of benefits. + References No definition available. + Details
Name: | ghm_DefinedBenefitPlanAdditionalDisclosuresAboutServiceAndAverageEarningsForCalculationOfBenefits
Namespace Prefix: | ghm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Annual decrement percentage in the defined benefit plan health care cost trend rate used to reach the ultimate health care cost trend rate. + References No definition available. + Details
Name: | ghm_DefinedBenefitPlanDecrementInHealthCareCostTrendRate
Namespace Prefix: | ghm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The increase in the defined benefit pension plan projected benefit obligation resulting from a change in the mortality table assumption. + References No definition available. + Details
Name: | ghm_DefinedBenefitPlanIncreaseInProjectedBenefitObligation
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of employee's first 3% salary deferral for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
Name: | ghm_DefinedContributionPlanEmployerMatchingPercentOnFirstThreePercentEmployeeSalaryDeferral
Namespace Prefix: | ghm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The employee deferral percentage that receives a 50% employer matching contribution. + References No definition available. + Details
Name: | ghm_DefinedContributionPlanSalaryDeferralPercentageThatReceivesAdditionalCompanyMatch
Namespace Prefix: | ghm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The employee salary deferral that receives 100% matching company contribution. + References No definition available. + Details
Name: | ghm_DefinedContributionPlanSalaryDeferralPercentageThatReceivesEquivalentCompanyMatch
Namespace Prefix: | ghm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Description of employer matching contributions to the 401K plan. + References No definition available. + Details
Name: | ghm_DescriptionOfEmployerMatchingContributionToFourHundredOneKPlan
Namespace Prefix: | ghm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighting in the mortality table assumption for male blue collar workers used in developing the defined benefit pension plan projected benefit obligation. + References No definition available. + Details
Name: | ghm_PercentageOfBlueCollarEmployees
Namespace Prefix: | ghm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The liability recognized in the balance sheet that is associated with the self insured medical plan. + References No definition available. + Details
Name: | ghm_SelfInsuredMedicalPlanLiability
Namespace Prefix: | ghm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Stop loss coverage amount per employee for each specific claim incurred. + References No definition available. + Details
Name: | ghm_SpecificStopLossInsuranceCoveragePerEmployee
Namespace Prefix: | ghm_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503844 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The interest rate used to adjust for the time value of money. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanFutureAmortizationOfGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount included in accumulated other comprehensive income (AOCI) related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanFutureAmortizationOfPriorServiceCostCredit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of decrease that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanSettlementsBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(8) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanSettlementsPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The ultimate trend rate for health care costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Year the ultimate health care cost trend rate is expected to be reached, in CCYY format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanYearThatRateReachesUltimateTrendRate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This item represents the amount of cash contributions during the period made by the entity to the Employee Stock Ownership Plan (ESOP). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929 + Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPCashContributionsToESOP
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Sum of the allocated, committed-to-be-released and suspense shares of the entity held by the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929 + Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition For a classified balance sheet, the amount recognized in balance sheet as a current liability associated with an underfunded defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Current Liabilities -URI http://asc.fasb.org/extlink&oid=6509677 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This represents the entire liability recognized in the balance sheet that is associated with the defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2417-114920 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.15) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2410-114920 + Details
Name: | us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_PlanNameAxis=ghm_DefinedContributionPlan401kMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=ghm_DefinedContributionPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |