Supplemental Financial Information (Schedule of Consolidating Statements of Comprehensive Income) (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 income	$ 20,619	$ 13,786	$ 37,384	$ 41,427
Other comprehensive income (loss):
Foreign currency translation adjustment	1,581	(193)	3,351	10,638
Adjustment to retirement benefit liability, net of tax	(2)	61	(8)	59
Adjustment to post employment health care benefit liability, net of tax	29	38	88	114
Other comprehensive income (loss)	1,608	(94)	3,431	10,811
Total comprehensive income	22,227	13,692	40,815	52,238
Guarantor Subsidiaries
Other comprehensive income (loss):
Foreign currency translation adjustment	0
Adjustment to retirement benefit liability, net of tax	(2)
Adjustment to post employment health care benefit liability, net of tax	29
Other comprehensive income (loss)	27
Total comprehensive income	23,238
Non-Guarantor Subsidiaries
Other comprehensive income (loss):
Foreign currency translation adjustment	1,581
Adjustment to retirement benefit liability, net of tax	0
Adjustment to post employment health care benefit liability, net of tax	0
Other comprehensive income (loss)	1,581
Total comprehensive income	1,874
Gibraltar Industries, Inc.
Other comprehensive income (loss):
Foreign currency translation adjustment	0
Adjustment to retirement benefit liability, net of tax	0
Adjustment to post employment health care benefit liability, net of tax	0
Other comprehensive income (loss)	0
Total comprehensive income	20,899
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	23,211	15,746	44,356	64,006
Other comprehensive income (loss):
Foreign currency translation adjustment		0	0	0
Adjustment to retirement benefit liability, net of tax		61	(8)	59
Adjustment to post employment health care benefit liability, net of tax		38	88	114
Other comprehensive income (loss)		99	80	173
Total comprehensive income		15,845	44,436	64,179
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	293	1,862	(1,747)	9,531
Other comprehensive income (loss):
Foreign currency translation adjustment		(193)	3,351	10,638
Adjustment to retirement benefit liability, net of tax		0	0	0
Adjustment to post employment health care benefit liability, net of tax		0	0	0
Other comprehensive income (loss)		(193)	3,351	10,638
Total comprehensive income		1,669	1,604	20,169
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net income	20,899	13,435	37,846	41,712
Other comprehensive income (loss):
Foreign currency translation adjustment		0	0	0
Adjustment to retirement benefit liability, net of tax		0	0	0
Adjustment to post employment health care benefit liability, net of tax		0	0	0
Other comprehensive income (loss)		0	0	0
Total comprehensive income		13,435	37,846	41,712
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net income	(23,784)	(17,257)	(43,071)	(73,822)
Other comprehensive income (loss):
Foreign currency translation adjustment	0	0	0	0
Adjustment to retirement benefit liability, net of tax	0	0	0	0
Adjustment to post employment health care benefit liability, net of tax	0	0	0	0
Other comprehensive income (loss)	0	0	0	0
Total comprehensive income	$ (23,784)	$ (17,257)	$ (43,071)	$ (73,822)