Basis of Presentation and Nature of Operations - Substantial Expenses in Connection with Acquisition (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
May 31, 2013
Business Acquisition [Line Items]
Internal labor	$ 3.0
LDACS [Member]
Business Acquisition [Line Items]
Internal labor	$ 0.3

Business Acquisition, Cost Of Acquired Entity, Internal Labor Costs

No definition available.

Name:	gy_BusinessAcquisitionCostOfAcquiredEntityInternalLaborCosts
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration