Supplemental Financial Information (Schedule of Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Schedule Of Supplemental Financial Information [Line Items]
Cash and cash equivalents	$ 173,062	$ 68,858	$ 43,331	$ 110,610	$ 43,331	$ 110,610
Accounts receivable, net	155,434	164,969
Intercompany balances	0	0
Inventories	92,778	107,058
Other current assets	9,897	10,537
Total current assets	431,171	351,422
Property, plant, and equipment, net	106,315	118,932
Goodwill	294,858	292,390
Acquired intangibles	118,388	123,013
Other assets	4,100	4,015
Investment in subsidiaries	0	0
Total assets	954,832	889,772
Accounts payable	87,495	89,204
Accrued expenses	63,111	67,605
Billings in excess of cost	26,026	28,186
Current maturities of long-term debt	400	400
Total current liabilities	177,032	185,395
Long-term debt	209,041	208,882
Deferred income taxes	43,366	42,654
Other non-current liabilities	55,748	42,755
Total shareholders’ equity	469,645	410,086
Total liabilities and shareholders' equity	954,832	889,772
Reportable Legal Entities | Gibraltar Industries, Inc.
Schedule Of Supplemental Financial Information [Line Items]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Intercompany balances	8,234	15,023
Inventories	0	0
Other current assets	12,808	4,535
Total current assets	21,042	19,558
Property, plant, and equipment, net	0	0
Goodwill	0	0
Acquired intangibles	0	0
Other assets	0	0
Investment in subsidiaries	660,635	603,208
Total assets	681,677	622,766
Accounts payable	0	0
Accrued expenses	4,116	5,127
Billings in excess of cost	0	0
Current maturities of long-term debt	0	0
Total current liabilities	4,116	5,127
Long-term debt	207,916	207,553
Deferred income taxes	0	0
Other non-current liabilities	0	0
Total shareholders’ equity	469,645	410,086
Total liabilities and shareholders' equity	681,677	622,766
Reportable Legal Entities | Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Cash and cash equivalents	149,784	39,597	18,886	91,466
Accounts receivable, net	146,258	142,674
Intercompany balances	(2,212)	12,033
Inventories	87,296	99,132
Other current assets	(8,672)	2,957
Total current assets	372,454	296,393
Property, plant, and equipment, net	100,968	106,413
Goodwill	270,017	270,017
Acquired intangibles	106,097	111,734
Other assets	4,100	4,015
Investment in subsidiaries	64,525	54,792
Total assets	918,161	843,364
Accounts payable	84,040	81,551
Accrued expenses	55,455	55,363
Billings in excess of cost	21,758	20,548
Current maturities of long-term debt	400	400
Total current liabilities	161,653	157,862
Long-term debt	1,125	1,329
Deferred income taxes	39,000	38,763
Other non-current liabilities	55,748	42,202
Total shareholders’ equity	660,635	603,208
Total liabilities and shareholders' equity	918,161	843,364
Reportable Legal Entities | Non-Guarantor Subsidiaries
Schedule Of Supplemental Financial Information [Line Items]
Cash and cash equivalents	23,278	29,261	24,445	19,144
Accounts receivable, net	9,176	22,295
Intercompany balances	(6,022)	(27,056)
Inventories	5,482	7,926
Other current assets	5,761	3,045
Total current assets	37,675	35,471
Property, plant, and equipment, net	5,347	12,519
Goodwill	24,841	22,373
Acquired intangibles	12,291	11,279
Other assets	0	0
Investment in subsidiaries	0	0
Total assets	80,154	81,642
Accounts payable	3,455	7,653
Accrued expenses	3,540	7,115
Billings in excess of cost	4,268	7,638
Current maturities of long-term debt	0	0
Total current liabilities	11,263	22,406
Long-term debt	0	0
Deferred income taxes	4,366	3,891
Other non-current liabilities	0	553
Total shareholders’ equity	64,525	54,792
Total liabilities and shareholders' equity	80,154	81,642
Eliminations
Schedule Of Supplemental Financial Information [Line Items]
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts receivable, net	0	0
Intercompany balances	0	0
Inventories	0	0
Other current assets	0	0
Total current assets	0	0
Property, plant, and equipment, net	0	0
Goodwill	0	0
Acquired intangibles	0	0
Other assets	0	0
Investment in subsidiaries	(725,160)	(658,000)
Total assets	(725,160)	(658,000)
Accounts payable	0	0
Accrued expenses	0	0
Billings in excess of cost		0
Current maturities of long-term debt	0	0
Total current liabilities	0	0
Long-term debt	0	0
Deferred income taxes	0	0
Other non-current liabilities	0	0
Total shareholders’ equity	(725,160)	(658,000)
Total liabilities and shareholders' equity	$ (725,160)	$ (658,000)