Inventory and Merchandise In Service - Additional Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Sep. 28, 2013
Inventory Disclosure [Abstract]
Effect of change in inventory lives on income from operations	$ 2,273
Effect of change in inventory lives on net income	$ 1,435
Effect of change in inventory lives on earnings per share (in dollars per share)	$ 0.07

The effect on basic and diluted earnings per share resulting from the change in inventory lives.

No definition available.

Name:	gk_EffectofChangeinInventoryLivesonEarningsPerShare
Namespace Prefix:	gk_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration