XML 81 R99.htm IDEA: XBRL DOCUMENT v2.4.0.8

Exit Activity Costs And Asset Impairments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012 item	Dec. 31, 2011 item
Exit Activity Costs And Asset Impairments [Abstract]
Number of consolidated facilities	2	2	3

X

- Definition

Number of consolidated facilities.

+ References

No definition available.

+ Details

Name:	rock_NumberOfConsolidatedFacilities
Namespace Prefix:	rock_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Details

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