XML 51 R55.htm IDEA: XBRL DOCUMENT
v3.19.3

Equity-Based Compensation (Performance Stock Units - Settled in Cash) (Details) - USD ($) $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Accrued equity based compensation |  | $ 27.0 | $ 38.4
Performance stock units |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Percentage of target performance stock units earned | 200.00% |  |
Units converted (in shares) | 256,000 |  |
Closing period | 90 days |  |
Non Current Liabilities |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Accrued equity based compensation |  | $ 22.0 | $ 23.6
Performance stock units |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
PSUs compensation expense | $ 8.9 |  |

X
- Definition Accrued Equity Based Compensation + References No definition available. + Details
Name: | rock_AccruedEquityBasedCompensation
Namespace Prefix: | rock_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage of performance stock units earned during performance period based on the terms of the performance stock unit award. + References No definition available. + Details
Name: | rock_EquityBasedCompensationPercentOfTargetedPerformanceStockUnitsEarned
Namespace Prefix: | rock_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Trailing Day Closing Price + References No definition available. + Details
Name: | rock_SharebasedCompensationArrangementbySharebasedPaymentAwardTrailingDayClosingPrice
Namespace Prefix: | rock_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -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=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 options vested. + References No definition available. + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=rock_NonCurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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