XML 20 R8.htm IDEA: XBRL DOCUMENT
v3.21.2

Consolidated Statement of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Sep. 30, 2021 | Jun. 30, 2021 | Mar. 31, 2021 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020
Statement of Stockholders' Equity [Abstract] |  |  |  |  |  |
Adjustment to pension benefit liability, taxes | $ 9 | $ 10 | $ 10 | $ 7 | $ 6 | $ 7

X
- Definition Other Comprehensive Income Minimum Post Retirement Benefit Plan, Net Adjustment Tax 1 + References No definition available. + Details
Name: | rock_OtherComprehensiveIncomeMinimumPostRetirementBenefitPlanNetAdjustmentTax1
Namespace Prefix: | rock_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_StatementOfStockholdersEquityAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration