XML 117 R101.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Equity-Based Compensation (Cash Paid to Settle Liability Awards) (Details) - USD ($) shares in Thousands, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
MSPP |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Restricted stock units credited | $ 3,137 | $ 1,901 | $ 2,120
Restricted stock units |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Restricted stock units credited | $ 198,155 | $ 94,047 | $ 119,105
Restricted stock units balance, vested and unvested | 646,669 | 519,668 | 647,371
Management |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
MSPP expense (in thousands) | $ 8,565 | $ 2,767 | $ 329

X
- Definition The amount of plan compensation cost recognized during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929 + Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cash paid related to share-based compensation liabilities. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of equity instruments other than options outstanding, including both vested and non-vested instruments. + 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 (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=rock_ManagementStockPurchasePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TitleOfIndividualAxis=us-gaap_ManagementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |