Supplemental Financial Information (Schedule of Consolidating Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	$ 274,574	$ 272,734	$ 728,806	$ 776,143
Cost of sales	205,839	204,847	548,991	585,263
Gross profit	68,735	67,887	179,815	190,880
Selling, general, and administrative expense	33,042	41,365	109,513	118,021
Income from operations	35,693	26,522	70,302	72,859
Interest expense	3,486	3,625	10,612	10,982
Other expense	404	159	811	8,319
Income before taxes	31,803	22,738	58,879	53,558
Provision for income taxes	11,184	8,952	21,090	12,131
Income from continuing operations	20,619	13,786	37,789	41,427
Loss from discontinued operations before taxes	0	0	(644)	0
Benefit of income taxes	0	0	(239)	0
Loss from discontinued operations	0	0	(405)	0
Equity in earnings from subsidiaries	0	0	0	0
Net income	20,619	13,786	37,384	41,427
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	264,448	265,657	700,848	728,782
Cost of sales	198,103	202,199	527,389	551,195
Gross profit	66,345	63,458	173,459	177,587
Selling, general, and administrative expense	31,003	38,505	101,190	99,622
Income from operations	35,342	24,953	72,269	77,965
Interest expense	105	241	459	836
Other expense	100	24	345	465
Income before taxes	35,137	24,688	71,465	76,664
Provision for income taxes	12,219	10,804	24,957	22,189
Income from continuing operations			46,508
Loss from discontinued operations before taxes			(644)
Benefit of income taxes			(239)
Loss from discontinued operations			(405)
Equity in earnings from subsidiaries	293	1,862	(1,747)	9,531
Net income	23,211	15,746	44,356	64,006
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	15,514	15,799	37,383	63,014
Cost of sales	12,844	11,721	30,565	49,436
Gross profit	2,670	4,078	6,818	13,578
Selling, general, and administrative expense	2,005	2,766	8,212	4,131
Income from operations	665	1,312	(1,394)	9,447
Interest expense	(21)	(19)	(54)	(61)
Other expense	304	(95)	466	(863)
Income before taxes	382	1,426	(1,806)	10,371
Provision for income taxes	89	(436)	(59)	840
Income from continuing operations			(1,747)
Loss from discontinued operations before taxes			0
Benefit of income taxes			0
Loss from discontinued operations			0
Equity in earnings from subsidiaries	0	0	0	0
Net income	293	1,862	(1,747)	9,531
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	0	0	0	0
Cost of sales	0	0	0	0
Gross profit	0	0	0	0
Selling, general, and administrative expense	34	94	111	14,268
Income from operations	(34)	(94)	(111)	(14,268)
Interest expense	3,402	3,403	10,207	10,207
Other expense	0	230	0	8,717
Income before taxes	(3,436)	(3,727)	(10,318)	(33,192)
Provision for income taxes	(1,124)	(1,416)	(3,808)	(10,898)
Income from continuing operations			(6,510)
Loss from discontinued operations before taxes			0
Benefit of income taxes			0
Loss from discontinued operations			0
Equity in earnings from subsidiaries	23,211	15,746	44,356	64,006
Net income	20,899	13,435	37,846	41,712
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net Sales	(5,388)	(8,722)	(9,425)	(15,653)
Cost of sales	(5,108)	(9,073)	(8,963)	(15,368)
Gross profit	(280)	351	(462)	(285)
Selling, general, and administrative expense	0	0	0	0
Income from operations	(280)	351	(462)	(285)
Interest expense	0	0	0	0
Other expense	0	0	0	0
Income before taxes	(280)	351	(462)	(285)
Provision for income taxes	0	0	0	0
Income from continuing operations			(462)
Loss from discontinued operations before taxes			0
Benefit of income taxes			0
Loss from discontinued operations			0
Equity in earnings from subsidiaries	(23,504)	(17,608)	(42,609)	(73,537)
Net income	$ (23,784)	$ (17,257)	$ (43,071)	$ (73,822)