Supplemental Financial Information (Consolidating Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Statement of Income Captions [Line Items]
Net income	$ 13,117	$ 19,503	$ 22,837	$ 8,352	$ 25,176	$ 20,619	$ 12,769	$ 3,996	$ 63,809	$ 62,560	$ 33,675
Other comprehensive income:
Foreign currency translation adjustment									(3,241)	3,150	6,945
Cumulative effect of accounting change (see Note 1)									(350)	0	0
Adjustment to pension and post-retirement benefit liability, net of tax									723	205	750
Other comprehensive (loss) income									(2,868)	3,355	7,695
Total comprehensive income									60,941	65,915	41,370
Gibraltar Industries, Inc.
Condensed Statement of Income Captions [Line Items]
Net income									64,637	63,584	32,998
Other comprehensive income:
Foreign currency translation adjustment									0	0	0
Cumulative effect of accounting change (see Note 1)									0
Adjustment to pension and post-retirement benefit liability, net of tax									0	0	0
Other comprehensive (loss) income									0	0	0
Total comprehensive income									64,637	63,584	32,998
Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income									74,544	72,261	57,857
Other comprehensive income:
Foreign currency translation adjustment									0	0	0
Cumulative effect of accounting change (see Note 1)									(350)
Adjustment to pension and post-retirement benefit liability, net of tax									723	205	750
Other comprehensive (loss) income									373	205	750
Total comprehensive income									74,917	72,466	58,607
Non-Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income									3,591	(943)	3,699
Other comprehensive income:
Foreign currency translation adjustment									(3,241)	3,150	6,945
Cumulative effect of accounting change (see Note 1)									0
Adjustment to pension and post-retirement benefit liability, net of tax									0	0	0
Other comprehensive (loss) income									(3,241)	3,150	6,945
Total comprehensive income									350	2,207	10,644
Eliminations
Condensed Statement of Income Captions [Line Items]
Net income									(78,963)	(72,342)	(60,879)
Other comprehensive income:
Foreign currency translation adjustment									0	0	0
Cumulative effect of accounting change (see Note 1)									0
Adjustment to pension and post-retirement benefit liability, net of tax									0	0	0
Other comprehensive (loss) income									0	0	0
Total comprehensive income									$ (78,963)	$ (72,342)	$ (60,879)