Supplemental Financial Information (Schedule of Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	$ 38,210	$ 48,831
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired	(5,241)	(18,494)
Net proceeds from sale of property and equipment	3,147	12,935
Purchases of property, plant, and equipment	(6,767)	(5,152)
Net cash used in investing activities	(8,861)	(10,711)
Cash Flows from Financing Activities
Long-term debt payments	(400)	(400)
Purchase of treasury stock at market prices	(6,549)	(1,982)
Net proceeds from issuance of common stock	1,343	649
Intercompany financing	0	0
Net cash used in financing activities	(5,606)	(1,733)
Effect of exchange rate changes on cash	(610)	1,468
Net increase in cash and cash equivalents	23,133	37,855
Cash and cash equivalents at beginning of year	222,280	170,177
Cash and cash equivalents at end of period	245,413	208,032
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	47,971	64,702
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired	(5,241)	(18,494)
Net proceeds from sale of property and equipment	3,044	12,935
Purchases of property, plant, and equipment	(6,537)	(4,929)
Net cash used in investing activities	(8,734)	(10,488)
Cash Flows from Financing Activities
Long-term debt payments	(400)	(400)
Purchase of treasury stock at market prices	0	0
Net proceeds from issuance of common stock	0	0
Intercompany financing	(17,474)	(14,813)
Net cash used in financing activities	(17,874)	(15,213)
Effect of exchange rate changes on cash	0	0
Net increase in cash and cash equivalents	21,363	39,001
Cash and cash equivalents at beginning of year	192,604
Cash and cash equivalents at end of period	213,967
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	3,479	(735)
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired	0	0
Net proceeds from sale of property and equipment	103	0
Purchases of property, plant, and equipment	(230)	(223)
Net cash used in investing activities	(127)	(223)
Cash Flows from Financing Activities
Long-term debt payments	0	0
Purchase of treasury stock at market prices	0	0
Net proceeds from issuance of common stock	0	0
Intercompany financing	(972)	(1,656)
Net cash used in financing activities	(972)	(1,656)
Effect of exchange rate changes on cash	(610)	1,468
Net increase in cash and cash equivalents	1,770	(1,146)
Cash and cash equivalents at beginning of year	29,676
Cash and cash equivalents at end of period	31,446
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net cash provided by (used in) operating activities	(13,240)	(15,136)
Cash Flows from Investing Activities
Cash paid for acquisitions, net of cash acquired	0	0
Net proceeds from sale of property and equipment	0	0
Purchases of property, plant, and equipment	0	0
Net cash used in investing activities	0	0
Cash Flows from Financing Activities
Long-term debt payments	0	0
Purchase of treasury stock at market prices	(6,549)	(1,982)
Net proceeds from issuance of common stock	1,343	649
Intercompany financing	18,446	16,469
Net cash used in financing activities	13,240	15,136
Effect of exchange rate changes on cash	0	0
Net increase 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	0
Net proceeds from sale of property and equipment	0	0
Purchases of property, plant, and equipment	0	0
Net cash used in investing activities	0	0
Cash Flows from Financing Activities
Long-term debt payments	0	0
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 increase 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