Supplemental Financial Information (Schedule of Consolidating Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Supplemental Financial Information [Line Items]
Net income	$ 13,786	$ 18,612	$ 9,029	$ 13,632	$ 27,641	$ 41,427	$ 23,228
Other comprehensive income (loss):
Foreign currency translation adjustment	(193)			(3,005)		10,638	(4,667)
Reclassification of loss on cash flow hedges, net of tax	0			0		0	143
Adjustment to retirement benefit liability, net of tax	61			3		59	7
Adjustment to post-retirement health care liability, net of tax	38			36		114	110
Other comprehensive (loss) income	(94)			(2,966)		10,811	(4,407)
Total comprehensive income	13,692			10,666		52,238	18,821
Gibraltar Industries, Inc.
Other comprehensive income (loss):
Foreign currency translation adjustment	0
Adjustment to retirement benefit liability, net of tax	0
Adjustment to post-retirement health care liability, net of tax	0
Other comprehensive (loss) income	0
Total comprehensive income	13,435
Guarantor Subsidiaries
Other comprehensive income (loss):
Foreign currency translation adjustment	0
Adjustment to retirement benefit liability, net of tax	61
Adjustment to post-retirement health care liability, net of tax	38
Other comprehensive (loss) income	99
Total comprehensive income	15,845
Non-Guarantor Subsidiaries
Other comprehensive income (loss):
Foreign currency translation adjustment	(193)
Adjustment to retirement benefit liability, net of tax	0
Adjustment to post-retirement health care liability, net of tax	0
Other comprehensive (loss) income	(193)
Total comprehensive income	1,669
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net income	13,435			15,503		41,712	25,553
Other comprehensive income (loss):
Foreign currency translation adjustment				0		0	0
Reclassification of loss on cash flow hedges, net of tax							0
Adjustment to retirement benefit liability, net of tax				0		0	0
Adjustment to post-retirement health care liability, net of tax				0		0	0
Other comprehensive (loss) income				0		0	0
Total comprehensive income				15,503		41,712	25,553
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	15,746			17,742		64,006	32,248
Other comprehensive income (loss):
Foreign currency translation adjustment				0		0	0
Reclassification of loss on cash flow hedges, net of tax							143
Adjustment to retirement benefit liability, net of tax				3		59	7
Adjustment to post-retirement health care liability, net of tax				36		114	110
Other comprehensive (loss) income				39		173	260
Total comprehensive income				17,781		64,179	32,508
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	1,862			1,411		9,531	1,959
Other comprehensive income (loss):
Foreign currency translation adjustment				(3,005)		10,638	(4,667)
Reclassification of loss on cash flow hedges, net of tax							0
Adjustment to retirement benefit liability, net of tax				0		0	0
Adjustment to post-retirement health care liability, net of tax				0		0	0
Other comprehensive (loss) income				(3,005)		10,638	(4,667)
Total comprehensive income				(1,594)		20,169	(2,708)
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net income	(17,257)			(21,024)		(73,822)	(36,532)
Other comprehensive income (loss):
Foreign currency translation adjustment	0			0		0	0
Reclassification of loss on cash flow hedges, net of tax							0
Adjustment to retirement benefit liability, net of tax	0			0		0	0
Adjustment to post-retirement health care liability, net of tax	0			0		0	0
Other comprehensive (loss) income	0			0		0	0
Total comprehensive income	$ (17,257)			$ (21,024)		$ (73,822)	$ (36,532)