Consolidated Statement of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Statement of Stockholders' Equity [Abstract]
Adjustment to pension benefit liability, taxes	$ 10	$ 10

Other Comprehensive Income Minimum Post Retirement Benefit Plan, Net Adjustment Tax 1

No definition available.

Name:	rock_OtherComprehensiveIncomeMinimumPostRetirementBenefitPlanNetAdjustmentTax1
Namespace Prefix:	rock_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration