XML 70 R58.htm IDEA: XBRL DOCUMENT v3.21.2

Exit Activity Costs and Asset Impairments (Narrative) (Details) - facility	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Number of facilities closed	2	1

X

- Definition

Restructuring and Related Cost, Number of Facilities to be Closed

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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