Supplemental Financial Information (Schedule of Consolidating Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule Of Supplemental Financial Information [Line Items]
Net income	$ 12,769	$ 18,612	$ 16,765	$ 27,641
Other comprehensive income (loss):
Foreign currency translation adjustment	1,091	7,753	1,770	10,831
Adjustment to retirement benefit liability, net of tax	(3)	(1)	(6)	(2)
Adjustment to post employment health care benefit liability, net of tax	30	38	59	76
Other comprehensive income	1,118	7,790	1,823	10,905
Total comprehensive income	13,887	26,402	18,588	38,546
Guarantor Subsidiaries
Other comprehensive income (loss):
Foreign currency translation adjustment	0
Adjustment to retirement benefit liability, net of tax	(3)
Adjustment to post employment health care benefit liability, net of tax	30
Other comprehensive income	27
Total comprehensive income	14,829
Non-Guarantor Subsidiaries
Other comprehensive income (loss):
Foreign currency translation adjustment	1,091
Adjustment to retirement benefit liability, net of tax	0
Adjustment to post employment health care benefit liability, net of tax	0
Other comprehensive income	1,091
Total comprehensive income	(257)
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	0
Total comprehensive income	12,705
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	14,802	36,764	21,145	48,260
Other comprehensive income (loss):
Foreign currency translation adjustment		0	0	0
Adjustment to retirement benefit liability, net of tax		(1)	(6)	(2)
Adjustment to post employment health care benefit liability, net of tax		38	59	76
Other comprehensive income		37	53	74
Total comprehensive income		36,801	21,198	48,334
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Net income	(1,348)	7,418	(2,040)	7,669
Other comprehensive income (loss):
Foreign currency translation adjustment		7,753	1,770	10,831
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		7,753	1,770	10,831
Total comprehensive income		15,171	(270)	18,500
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Net income	12,705	18,971	16,947	28,277
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		0	0	0
Total comprehensive income		18,971	16,947	28,277
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Net income	(13,390)	(44,541)	(19,287)	(56,565)
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	0	0	0	0
Total comprehensive income	$ (13,390)	$ (44,541)	$ (19,287)	$ (56,565)