XML 139 R116.htm IDEA: XBRL DOCUMENT v3.10.0.1

Supplemental Financial Information (Narrative) (Details)	Dec. 31, 2018	Dec. 31, 2017	Jan. 31, 2013
Senior Subordinated 6.25% Notes
Debt Instrument [Line Items]
Senior Subordinated Notes, interest rate	6.25%	6.25%	6.25%

X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_DebtInstrumentAxis=rock_SeniorSubordinatedSixPointTwoFivePercentNotesDueFebruaryOneTwoThousandTwentyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: