Name:	gk_ActualMinimumInterestCoverageRatio
Namespace Prefix:	gk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

The actual net worth is calculated as the total stockholders' equity balance of the firm as of the reporting period.

No definition available.

Name:	gk_ActualMinimumNetWorth
Namespace Prefix:	gk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The actual leverage ratio is calculated as the ratio of total debt including letters of credit as of the reporting period date as compared to trailing twelve month consolidated total EBITDA.

No definition available.

Name:	gk_LeverageRatioActualMaximum
Namespace Prefix:	gk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

The required maximum leverage ratio is calculated as the ratio of total debt including letters of credit as of the reporting period date as compared to trailing twelve month consolidated total EBITDA.

No definition available.

Name:	gk_MaximumLeverageRatioRequired
Namespace Prefix:	gk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

The required minimum interest coverage ratio is calculated as the ratio of consolidated EBITDA for the four consecutive quarters as compared to consolidated interest expense for the same period.

No definition available.

Name:	gk_RequiredMinimumInterestCoverageRatio
Namespace Prefix:	gk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Details

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

The lowest amount of net worth (total assets minus total liabilities) required by secondary market investors or state-imposed regulatory mandates.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (c)(a)

-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998