Supplemental Financial Information (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	$ (22,206)	$ 2,343
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired	0	(18,561)
Net proceeds from sale of property and equipment	2,823	9,233
Purchases of property, plant, and equipment	(1,033)	(1,453)
Net cash provided by (used in) investing activities	1,790	(10,781)
Cash Flows from Financing Activities
Purchase of treasury stock at market prices	(850)	(922)
Net proceeds from issuance of common stock	226	11
Intercompany financing	0	0
Net cash used in financing activities	(624)	(911)
Effect of exchange rate changes on cash	(499)	73
Net decrease in cash and cash equivalents	(21,539)	(9,276)
Cash and cash equivalents at beginning of year	222,280
Cash and cash equivalents at end of period	200,741
Reportable Legal Entities \| Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	(14,829)	12,141
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired		(18,561)
Net proceeds from sale of property and equipment	2,823	9,081
Purchases of property, plant, and equipment	(1,008)	(1,326)
Net cash provided by (used in) investing activities	1,815	(10,806)
Cash Flows from Financing Activities
Purchase of treasury stock at market prices	0	0
Net proceeds from issuance of common stock	0	0
Intercompany financing	(6,660)	(6,398)
Net cash used in financing activities	(6,660)	(6,398)
Effect of exchange rate changes on cash	0	0
Net decrease in cash and cash equivalents	(19,674)	(5,063)
Cash and cash equivalents at beginning of year	192,604
Cash and cash equivalents at end of period	172,930
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	(771)	(3,193)
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired		0
Net proceeds from sale of property and equipment	0	152
Purchases of property, plant, and equipment	(25)	(127)
Net cash provided by (used in) investing activities	(25)	25
Cash Flows from Financing Activities
Purchase of treasury stock at market prices	0	0
Net proceeds from issuance of common stock	0	0
Intercompany financing	(570)	(1,118)
Net cash used in financing activities	(570)	(1,118)
Effect of exchange rate changes on cash	(499)	73
Net decrease in cash and cash equivalents	(1,865)	(4,213)
Cash and cash equivalents at beginning of year	29,676
Cash and cash equivalents at end of period	27,811
Reportable Legal Entities \| Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	(6,606)	(6,605)
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired		0
Net proceeds from sale of property and equipment	0	0
Purchases of property, plant, and equipment	0	0
Net cash provided by (used in) investing activities	0	0
Cash Flows from Financing Activities
Purchase of treasury stock at market prices	(850)	(922)
Net proceeds from issuance of common stock	226	11
Intercompany financing	7,230	7,516
Net cash used in financing activities	6,606	6,605
Effect of exchange rate changes on cash	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of year	0
Cash and cash equivalents at end of period	0
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	0	0
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired		0
Net proceeds from sale of property and equipment	0	0
Purchases of property, plant, and equipment	0	0
Net cash provided by (used in) investing activities	0	0
Cash Flows from Financing Activities
Purchase of treasury stock at market prices	0	0
Net proceeds from issuance of common stock	0	0
Intercompany financing	0	0
Net cash used in financing activities	0	0
Effect of exchange rate changes on cash	0	0
Net decrease in cash and cash equivalents	0	$ 0
Cash and cash equivalents at beginning of year	0
Cash and cash equivalents at end of period	$ 0

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Schedule Of Supplemental Financial Information [Line Items]

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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