Supplemental Financial Information (Consolidating Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Net sales	$ 258,112	$ 274,574	$ 247,627	$ 206,605	$ 231,838	$ 272,734	$ 265,738	$ 237,671	$ 986,918	$ 1,007,981	$ 1,040,873
Cost of sales									750,374	763,219	853,897
Gross profit	56,729	68,735	61,825	49,255	53,882	67,887	68,843	54,150	236,544	244,762	186,976
Selling, general, and administrative expense									143,448	161,099	133,381
Intangible asset impairment									247	10,175	4,863
Income from operations	22,547	35,693	24,930	9,679	629	26,522	28,576	17,761	92,849	73,488	48,732
Interest expense	3,420	3,486	3,550	3,576	3,595	3,625	3,666	3,691	14,032	14,577	15,003
Other expense (income)									909	8,928	(3,371)
Income before taxes									77,908	49,983	37,100
Provision for income taxes									14,943	16,264	13,624
Income from continuing operations	25,176	20,619	13,174	3,996	(7,708)	13,786	18,612	9,029	62,965	33,719	23,476
Loss before taxes									(644)	(70)	(44)
Benefit of income taxes									(239)	(26)	(16)
Loss from discontinued operations	0	0	(405)	0	(44)	0	0	0	(405)	(44)	(28)
Equity in earnings from subsidiaries									0	0	0
Net income	$ 25,176	$ 20,619	$ 12,769	$ 3,996	$ (7,752)	$ 13,786	$ 18,612	$ 9,029	62,560	33,675	23,448
Gibraltar Industries, Inc.
Condensed Income Statements, Captions [Line Items]
Net sales									0	0	0
Cost of sales									0	0	0
Gross profit									0	0	0
Selling, general, and administrative expense									147	14,302	133
Intangible asset impairment									0	0	0
Income from operations									(147)	(14,302)	(133)
Interest expense									13,609	13,609	13,609
Other expense (income)									0	8,716	50
Income before taxes									(13,756)	(36,627)	(13,792)
Provision for income taxes									(5,079)	(11,768)	(4,427)
Income from continuing operations									(8,677)	(24,859)	(9,365)
Loss before taxes									0	0	0
Benefit of income taxes									0	0	0
Loss from discontinued operations									0	0	0
Equity in earnings from subsidiaries									72,261	57,857	36,401
Net income									63,584	32,998	27,036
Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net sales									947,604	950,945	960,614
Cost of sales									719,587	722,315	785,085
Gross profit									228,017	228,630	175,529
Selling, general, and administrative expense									133,409	137,343	115,882
Intangible asset impairment									200	7,980	4,863
Income from operations									94,408	83,307	54,784
Interest expense									512	1,042	1,469
Other expense (income)									500	512	(3,154)
Income before taxes									93,396	81,753	56,469
Provision for income taxes									19,787	27,551	18,827
Income from continuing operations									73,609	54,202	37,642
Loss before taxes									(644)	(70)	(44)
Benefit of income taxes									(239)	(26)	(16)
Loss from discontinued operations									(405)	(44)	(28)
Equity in earnings from subsidiaries									(943)	3,699	(1,213)
Net income									72,261	57,857	36,401
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net sales									52,738	78,184	109,984
Cost of sales									43,187	62,729	94,949
Gross profit									9,551	15,455	15,035
Selling, general, and administrative expense									9,892	9,454	17,366
Intangible asset impairment									47	2,195	0
Income from operations									(388)	3,806	(2,331)
Interest expense									(89)	(74)	(75)
Other expense (income)									409	(300)	(267)
Income before taxes									(708)	4,180	(1,989)
Provision for income taxes									235	481	(776)
Income from continuing operations									(943)	3,699	(1,213)
Loss before taxes									0	0	0
Benefit of income taxes									0	0	0
Loss from discontinued operations									0	0	0
Equity in earnings from subsidiaries									0	0	0
Net income									(943)	3,699	(1,213)
Eliminations
Condensed Income Statements, Captions [Line Items]
Net sales									(13,424)	(21,148)	(29,725)
Cost of sales									(12,400)	(21,825)	(26,137)
Gross profit									(1,024)	677	(3,588)
Selling, general, and administrative expense									0	0	0
Intangible asset impairment									0	0	0
Income from operations									(1,024)	677	(3,588)
Interest expense									0	0	0
Other expense (income)									0	0	0
Income before taxes									(1,024)	677	(3,588)
Provision for income taxes									0	0	0
Income from continuing operations									(1,024)	677	(3,588)
Loss before taxes									0	0	0
Benefit of income taxes									0	0	0
Loss from discontinued operations									0	0	0
Equity in earnings from subsidiaries									(71,318)	(61,556)	(35,188)
Net income									$ (72,342)	$ (60,879)	$ (38,776)