Supplemental Financial Information (Schedule of Consolidating Statements of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	$ 200,615us-gaap_SalesRevenueNet	$ 191,032us-gaap_SalesRevenueNet
Cost of sales	170,700us-gaap_CostOfRevenue	161,168us-gaap_CostOfRevenue
Gross profit	29,915us-gaap_GrossProfit	29,864us-gaap_GrossProfit
Selling, general, and administrative expense	20,945	29,531
Income from operations	8,970us-gaap_OperatingIncomeLoss	333us-gaap_OperatingIncomeLoss
Interest expense	3,700us-gaap_InterestExpense	3,640us-gaap_InterestExpense
Other (income) expense	(3,559)us-gaap_OtherNonoperatingIncomeExpense	30us-gaap_OtherNonoperatingIncomeExpense
Income (loss) before taxes	8,829	(3,337)
Provision for (benefit of) income taxes	3,292us-gaap_IncomeTaxExpenseBenefit	(1,251)us-gaap_IncomeTaxExpenseBenefit
Income (loss) from continuing operations	5,537	(2,086)
Loss before taxes	(44)	0
Benefit of income taxes	(16)	0
Loss from discontinued operations	(28)	0
Equity in earnings from subsidiaries	0rock_EquityEarningsFromSubsidiaries	0rock_EquityEarningsFromSubsidiaries
Net income (loss)	5,509us-gaap_NetIncomeLoss	(2,086)us-gaap_NetIncomeLoss
Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling, general, and administrative expense	40	36
Income from operations	(40)	(36)
Interest expense	3,402	3,361
Other (income) expense	7	0
Income (loss) before taxes	(3,449)	(3,397)
Provision for (benefit of) income taxes	(1,210)	(1,177)
Income (loss) from continuing operations	(2,239)	(2,220)
Loss before taxes	0
Benefit of income taxes	0
Loss from discontinued operations	0
Equity in earnings from subsidiaries	7,851	315
Net income (loss)	5,612	(1,905)
Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	184,350	172,781
Cost of sales	156,864	145,161
Gross profit	27,486	27,620
Selling, general, and administrative expense	19,362	27,763
Income from operations	8,124	(143)
Interest expense	327	314
Other (income) expense	(3,523)	30
Income (loss) before taxes	11,320	(487)
Provision for (benefit of) income taxes	4,261	(234)
Income (loss) from continuing operations	7,059	(253)
Loss before taxes	(44)
Benefit of income taxes	(16)
Loss from discontinued operations	(28)
Equity in earnings from subsidiaries	820	568
Net income (loss)	7,851	315
Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	19,748	22,919
Cost of sales	17,216	20,494
Gross profit	2,532	2,425
Selling, general, and administrative expense	1,543	1,732
Income from operations	989	693
Interest expense	(29)	(35)
Other (income) expense	(43)	0
Income (loss) before taxes	1,061	728
Provision for (benefit of) income taxes	241	160
Income (loss) from continuing operations	820	568
Loss before taxes	0
Benefit of income taxes	0
Loss from discontinued operations	0
Equity in earnings from subsidiaries	0	0
Net income (loss)	820	568
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	(3,483)	(4,668)
Cost of sales	(3,380)	(4,487)
Gross profit	(103)	(181)
Selling, general, and administrative expense	0	0
Income from operations	(103)	(181)
Interest expense	0	0
Other (income) expense	0	0
Income (loss) before taxes	(103)	(181)
Provision for (benefit of) income taxes	0	0
Income (loss) from continuing operations	(103)	(181)
Loss before taxes	0
Benefit of income taxes	0
Loss from discontinued operations	0
Equity in earnings from subsidiaries	(8,671)	(883)
Net income (loss)	$ (8,774)	$ (1,064)

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The aggregate cost of goods produced and sold and services rendered during the reporting period.

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Overall income (loss) from a disposal group that is classified as a component of the entity, before income tax, reported as a separate component of income before extraordinary items. Includes the following (before income tax): income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Tax effect allocated to a disposal group that is classified as a component of the entity reported as a separate component of income before extraordinary items. Includes the tax effects of the following: income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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