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:	na
Period Type:	duration

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 net worth is calculated as the sum of $375,000,000 plus 35% of the consolidated net income (if positive) for such fiscal quarter.

No definition available.

Name:	gk_MinimumNetWorthRequired
Namespace Prefix:	gk_
Data Type:	xbrli:monetaryItemType
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.