Graham Corporation Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Additional Information (Detail)

Employee Benefit Plans - Additional Information (Detail) (USD $) Share data in Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
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%ghm_PercentageOfBlueCollarEmployees
Increase in projected benefit obligations	$ 2,145,000
Accumulated benefit obligation	33,998,000	28,254,000
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 equal to employee salary deferral	100.00%
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	2021
Medical care cost trend rate decrements	0.50%
Current portion of accrued postretirement benefit obligation	92,000	98,000
Employee stock ownership plan, shares	233	252
Company contributions to the ESOP	0	0	0
Stop loss coverage per employee for claims	100,000
Maximum aggregate stop loss coverage	1,000,000
Total plan amount	3,738,000
Self-Insured medical plan liability	446,000ghm_SelfInsuredMedicalPlanLiability	221,000ghm_SelfInsuredMedicalPlanLiability
Defined Contribution Plan 401K [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined contribution plan	940,000	831,000	753,000
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated net actuarial loss for pension plan	1,174,000
Estimated prior service cost for pension plan	0
Pension expense	(469,000)	213,000	248,000
Weighted average discount rate used to develop net postretirement benefit cost	4.46%	4.28%	4.76%
Defined Contribution Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined contribution plan	294,000	257,000	204,000
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension expense	70,000	70,000	24,000
Pension expense related liability	341,000	298,000
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	38,000
Estimated prior service cost for pension plan	0
Pension expense	$ (40,000)	$ (87,000)	$ (83,000)
Weighted average discount rate used to develop net postretirement benefit cost	3.59%	3.26%	3.96%