Quarterly report pursuant to Section 13 or 15(d)

Product Warranty Liability - Additional Information (Detail)

v2.4.1.9
Product Warranty Liability - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Guarantees [Abstract]        
Income for product warranties $ 436ghm_ProductWarrantyIncomeExpense $ (47)ghm_ProductWarrantyIncomeExpense $ 573ghm_ProductWarrantyIncomeExpense $ 11ghm_ProductWarrantyIncomeExpense