Supplemental Financial Information (Schedule of Consolidating Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule Of Supplemental Financial Information [Line Items]
Net income	$ 22,837	$ 12,769	$ 31,189	$ 16,765
Other comprehensive (loss) income:
Foreign currency translation adjustment	(1,787)	1,091	(1,677)	1,770
Cumulative effect of accounting change (see Note 2)			(350)
Adjustment to retirement benefit liability, net of tax	(5)	(3)	(10)	(6)
Adjustment to post employment health care benefit liability, net of tax	31	30	63	59
Other comprehensive (loss) income	(1,761)	1,118	(1,974)	1,823
Total comprehensive income	21,076	13,887	29,215	18,588
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	25,518	14,802	36,488	21,145
Other comprehensive (loss) income:
Foreign currency translation adjustment	0	0	0	0
Cumulative effect of accounting change (see Note 2)			(350)
Adjustment to retirement benefit liability, net of tax	(5)	(3)	(10)	(6)
Adjustment to post employment health care benefit liability, net of tax	31	30	63	59
Other comprehensive (loss) income	26	27	(297)	53
Total comprehensive income	25,544	14,829	36,191	21,198
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	1,334	(1,348)	2,424	(2,040)
Other comprehensive (loss) income:
Foreign currency translation adjustment	(1,787)	1,091	(1,677)	1,770
Cumulative effect of accounting change (see Note 2)			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 (loss) income	(1,787)	1,091	(1,677)	1,770
Total comprehensive income	(453)	(257)	747	(270)
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net income	23,042	12,705	31,531	16,947
Other comprehensive (loss) income:
Foreign currency translation adjustment	0	0	0	0
Cumulative effect of accounting change (see Note 2)			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 (loss) income	0	0	0	0
Total comprehensive income	23,042	12,705	31,531	16,947
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net income	(27,057)	(13,390)	(39,254)	(19,287)
Other comprehensive (loss) income:
Foreign currency translation adjustment	0	0	0	0
Cumulative effect of accounting change (see Note 2)			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 (loss) income	0	0	0	0
Total comprehensive income	$ (27,057)	$ (13,390)	$ (39,254)	$ (19,287)