Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount

No definition available.

Name:	gk_EffectiveIncomeTaxRateReconciliationSharebasedCompensationExcessTaxBenefitAmount
Namespace Prefix:	gk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

+ Details

Name:	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 28A
-URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1500-109256

+ Details

Name:	us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AdditionalPaidInCapitalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_NewAccountingPronouncementEarlyAdoptionAxis=us-gaap_NewAccountingPronouncementEarlyAdoptionEffectMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=gk_AccountingStandardsUpdate201609Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

New Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 01, 2016	Sep. 26, 2015	Jul. 02, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect of adoption of share-based compensation accounting guidance			$ 836
Income tax benefit realized	$ 823
Increase in weighted average diluted shares outstanding	342,000	274,000
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect of adoption of share-based compensation accounting guidance			604
Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect of adoption of share-based compensation accounting guidance			$ 232
New Accounting Pronouncement, Early Adoption, Effect \| Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in weighted average diluted shares outstanding	102,000
New Accounting Pronouncement, Early Adoption, Effect \| Accounting Standards Update 2016-09 \| Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect of adoption of share-based compensation accounting guidance	$ 604
New Accounting Pronouncement, Early Adoption, Effect \| Accounting Standards Update 2016-09 \| Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect of adoption of share-based compensation accounting guidance	$ (604)