Defined benefit plan Period of payment of withdrawal liability.

No definition available.

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- Definition

Estimated share of undiscounted, unfunded vested benefits under all the MEPPs.

+ References

No definition available.

+ Details

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Namespace Prefix:	gk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of locations that discontinued participation in the Central States MEPP due to negotiations.

+ References

No definition available.

+ Details

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Namespace Prefix:	gk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of locations still participating in the Central States MEPP

+ References

No definition available.

+ Details

Name:	gk_LocationToParticipateInCentralStatesMepp
Namespace Prefix:	gk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Expenses incurred related to the withdrawal from multi-employer pension plans, including incentives for union participants, and other associated expenses.

+ References

No definition available.

+ Details

Name:	gk_PensionWithdrawalAndAssociatedExpenses
Namespace Prefix:	gk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of locations that discontinued participation in the Central States MEPP due to redundant facilities branch closures.

+ References

No definition available.

+ Details

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Namespace Prefix:	gk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Employee Benefit Plans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 29, 2012 Location	Mar. 31, 2012 Location	Dec. 29, 2012 Location
Multiemployer Plans [Line Items]
Location to discontinue our participation in Central States MEPP	2	2
Redundant branch facilities closed		2
Remaining location participating in Central States MEPP			1
Period of payment of withdrawal liability		20 years
Pension withdrawal and associated expenses		$ 24.0
Multi-Employer Pension Plans [Member] \| Minimum [Member]
Multiemployer Plans [Line Items]
Estimated share of undiscounted, unfunded vested benefits under all the MEPPs			3.0
Multi-Employer Pension Plans [Member] \| Maximum [Member]
Multiemployer Plans [Line Items]
Estimated share of undiscounted, unfunded vested benefits under all the MEPPs			4.0
Pension Plan [Member]
Multiemployer Plans [Line Items]
Employer contribution for pension plan			3.5