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Intangible Assets (Tables) | 12 Months Ended
--- | ---
Mar. 31, 2013
Intangible Assets [Abstract] |
Summary of intangible assets |
|  | Gross Carrying Amount |  |  | Accumulated Amortization |  |  | Net Carrying Amount |
At March 31, 2013 |  |  |  |  |  |  |  |  |  |  |  |
Intangibles subject to amortization: |  |  |  |  |  |  |  |  |  |  |  |
Backlog |  | $ | 170 |  |  | $ | 170 |  |  | $ | — |
Customer relationships |  |  | 2,700 |  |  |  | 412 |  |  |  | 2,288 |
|  | $ | 2,870 |  |  | $ | 582 |  |  | $ | 2,288 |
Intangibles not subject to amortization: |  |  |  |  |  |  |  |  |  |  |  |
Permits |  | $ | 10,300 |  |  | $ | — |  |  | $ | 10,300 |
Tradename |  |  | 2,500 |  |  |  | — |  |  |  | 2,500 |
|  | $ | 12,800 |  |  | $ | — |  |  | $ | 12,800 |
At March 31, 2012 |  |  |  |  |  |  |  |  |  |  |  |
Intangibles subject to amortization: |  |  |  |  |  |  |  |  |  |  |  |
Backlog |  | $ | 170 |  |  | $ | 170 |  |  | $ | — |
Customer relationships |  |  | 2,700 |  |  |  | 232 |  |  |  | 2,468 |
|  | $ | 2,870 |  |  | $ | 402 |  |  | $ | 2,468 |
Intangibles not subject to amortization: |  |  |  |  |  |  |  |  |  |  |  |
Permits |  | $ | 10,300 |  |  | $ | — |  |  | $ | 10,300 |
Tradename |  |  | 2,500 |  |  |  | — |  |  |  | 2,500 |
|  | $ | 12,800 |  |  | $ | — |  |  | $ | 12,800 |

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- Definition Tabular disclosure of assets, excluding financial assets and goodwill, lacking physical substance with a finite and indefinite life, by major class. + References No definition available. + Details
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Namespace Prefix: | ghm_
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- Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
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