Supplemental Financial Information (Consolidating Statements of Comprehensive Income) (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 Statement of Income Captions [Line Items]
Net income	$ 25,176	$ 20,619	$ 12,769	$ 3,996	$ (7,752)	$ 13,786	$ 18,612	$ 9,029	$ 62,560	$ 33,675	$ 23,448
Other comprehensive income:
Foreign currency translation adjustment									3,150	6,945	(6,228)
Unrealized loss on cash flow hedges, net of tax									0	0	143
Adjustment to retirement benefit liability, net of tax									(9)	55	49
Adjustment to post-retirement healthcare benefit liability, net of tax									214	695	171
Other comprehensive income (loss)									3,355	7,695	(5,865)
Total comprehensive income									65,915	41,370	17,583
Gibraltar Industries, Inc.
Condensed Statement of Income Captions [Line Items]
Net income									63,584	32,998	27,036
Other comprehensive income:
Foreign currency translation adjustment									0	0	0
Unrealized loss on cash flow hedges, net of tax											0
Adjustment to retirement benefit liability, net of tax									0	0	0
Adjustment to post-retirement healthcare benefit liability, net of tax									0	0	0
Other comprehensive income (loss)									0	0	0
Total comprehensive income									63,584	32,998	27,036
Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income									72,261	57,857	36,401
Other comprehensive income:
Foreign currency translation adjustment									0	0	0
Unrealized loss on cash flow hedges, net of tax											143
Adjustment to retirement benefit liability, net of tax									(9)	55	34
Adjustment to post-retirement healthcare benefit liability, net of tax									214	695	171
Other comprehensive income (loss)									205	750	348
Total comprehensive income									72,466	58,607	36,749
Non-Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income									(943)	3,699	(1,213)
Other comprehensive income:
Foreign currency translation adjustment									3,150	6,945	(6,228)
Unrealized loss on cash flow hedges, net of tax											0
Adjustment to retirement benefit liability, net of tax									0	0	15
Adjustment to post-retirement healthcare benefit liability, net of tax									0	0	0
Other comprehensive income (loss)									3,150	6,945	(6,213)
Total comprehensive income									2,207	10,644	(7,426)
Eliminations
Condensed Statement of Income Captions [Line Items]
Net income									(72,342)	(60,879)	(38,776)
Other comprehensive income:
Foreign currency translation adjustment									0	0	0
Unrealized loss on cash flow hedges, net of tax											0
Adjustment to retirement benefit liability, net of tax									0	0	0
Adjustment to post-retirement healthcare benefit liability, net of tax									0	0	0
Other comprehensive income (loss)									0	0	0
Total comprehensive income									$ (72,342)	$ (60,879)	$ (38,776)