Segment Information - Breakdown of Net Sales by Geographic Area (Detail) (USD $) In Thousands, unless otherwise specified
|
3 Months Ended |
12 Months Ended |
Mar. 31, 2015
|
Dec. 31, 2014
|
Sep. 30, 2014
|
Jun. 30, 2014
|
Mar. 31, 2014
|
Dec. 31, 2013
|
Sep. 30, 2013
|
Jun. 30, 2013
|
Mar. 31, 2015
|
Mar. 31, 2014
|
Mar. 31, 2013
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
$ 37,455us-gaap_SalesRevenueNet
|
$ 33,646us-gaap_SalesRevenueNet
|
$ 35,566us-gaap_SalesRevenueNet
|
$ 28,502us-gaap_SalesRevenueNet
|
$ 26,087us-gaap_SalesRevenueNet
|
$ 23,385us-gaap_SalesRevenueNet
|
$ 24,490us-gaap_SalesRevenueNet
|
$ 28,256us-gaap_SalesRevenueNet
|
$ 135,169us-gaap_SalesRevenueNet
|
$ 102,218us-gaap_SalesRevenueNet
|
$ 104,973us-gaap_SalesRevenueNet
|
Africa [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
237us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_AfricaMember
|
152us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_AfricaMember
|
235us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_AfricaMember
|
Asia [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
11,253us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_AsiaMember
|
11,486us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_AsiaMember
|
17,048us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_AsiaMember
|
Australia & New Zealand [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
330us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = ghm_AustraliaAndNewZealandMember
|
307us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = ghm_AustraliaAndNewZealandMember
|
29us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = ghm_AustraliaAndNewZealandMember
|
Canada [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
15,807us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_CA
|
11,419us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_CA
|
7,084us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_CA
|
Central America [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
1,772us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_CentralAmericaMember
|
3,210us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_CentralAmericaMember
|
4,633us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_CentralAmericaMember
|
Europe [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
943us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_EuropeMember
|
2,091us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_EuropeMember
|
2,027us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_EuropeMember
|
Mexico [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
407us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_MX
|
728us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_MX
|
89us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_MX
|
Middle East [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
10,155us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_MiddleEastMember
|
4,350us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_MiddleEastMember
|
14,834us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_MiddleEastMember
|
South America [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
7,866us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_SouthAmericaMember
|
4,625us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_SouthAmericaMember
|
3,299us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = us-gaap_SouthAmericaMember
|
U.S. [Member] |
|
|
|
|
|
|
|
|
|
|
|
Segment Reporting Information [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
Net sales |
|
|
|
|
|
|
|
|
$ 86,399us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_US
|
$ 63,850us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_US
|
$ 55,695us-gaap_SalesRevenueNet / us-gaap_StatementGeographicalAxis = country_US
|