Income Taxes - Year of Expiration for Company's State Net Operating Loss Carryforwards (Detail) (State [Member], USD $) In Millions, unless otherwise specified	Nov. 30, 2012
State [Member]
Operating Loss Carryforwards [Line Items]
2013	$ 0.2
2014	1.7
2015	24.7
2016	28.9
2017	30.0
2018	48.3
2019	105.5
Total	$ 239.3

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwards
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year Five

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearFive
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year Four

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearFour
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year One

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearOne
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year Seven

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearSeven
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year Six

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearSix
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year Three

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearThree
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Expiration Amount Of State And Foreign Net Operating Loss Carryforwards Year Two

No definition available.

Name:	gy_ExpirationAmountOfStateAndForeignNetOperatingLossCarryforwardsYearTwo
Namespace Prefix:	gy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	us-gaap_OperatingLossCarryforwardsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration