XML 106 R88.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Equity-Based Compensation (Summary of Compensation Expense Connection with Awards) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Share-based Compensation [Abstract] |  |  |
Expense recognized under the Prior Plan | $ 1,059 | $ 1,937 | $ 1,953
Expense recognized under the Plan | 5,643 | 3,993 | 1,938
Expense recognized under the Non-Employee Directors Plan | 420 | 443 | 0
Total stock compensation expense | 7,122 | 6,373 | 3,891
Tax benefits recognized related to stock compensation expense | $ 2,133 | $ 2,485 | $ 1,518

X
- Definition Share-Based Goods and Nonemployee Services Transaction, Share-based Compensation + References No definition available. + Details
Name: | rock_ShareBasedGoodsandNonemployeeServicesTransactionSharebasedCompensation
Namespace Prefix: | rock_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Stock Compensation Expense Recognized Under Equity Incentive Plan + References No definition available. + Details
Name: | rock_StockCompensationExpenseRecognizedUnderEquityIncentivePlan
Namespace Prefix: | rock_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Stock compensation expense recognized under terminated plans. + References No definition available. + Details
Name: | rock_StockCompensationExpenseRecognizedUnderTerminatedPlans
Namespace Prefix: | rock_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 + Details
Name: | us-gaap_ShareBasedCompensation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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