Supplemental Financial Information (Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 222,280	$ 170,177	$ 68,858	$ 110,610
Accounts receivable, net	145,385	124,072
Intercompany balances	0	0
Inventories	86,372	89,612
Other current assets	8,727	7,336
Total current assets	462,764	391,197
Property, plant, and equipment, net	97,098	108,304
Goodwill	321,074	304,032	292,390
Acquired intangibles	105,768	110,790
Other assets	4,681	3,922
Investment in subsidiaries	0	0
Total assets	991,385	918,245	889,772
Current liabilities:
Accounts payable	82,387	69,944
Accrued expenses	75,467	70,392
Billings in Excess of Cost	12,779	11,352
Current maturities of long-term debt	400	400
Total current liabilities	171,033	152,088
Long-term debt	209,621	209,237
Deferred income taxes	31,237	38,002
Other non-current liabilities	47,775	58,038
Total shareholders’ equity	531,719	460,880	410,086	387,229
Total liabilities and shareholders' equity	991,385	918,245
Gibraltar Industries, Inc.
Current assets:
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Intercompany balances	324	(615)
Inventories	0	0
Other current assets	5,415	13,783
Total current assets	5,739	13,168
Property, plant, and equipment, net	0	0
Goodwill	0	0
Acquired intangibles	0	0
Other assets	0	0
Investment in subsidiaries	739,970	663,118
Total assets	745,709	676,286
Current liabilities:
Accounts payable	0	0
Accrued expenses	5,469	7,369
Billings in Excess of Cost	0	0
Current maturities of long-term debt	0	0
Total current liabilities	5,469	7,369
Long-term debt	208,521	208,037
Deferred income taxes	0	0
Other non-current liabilities	0	0
Total shareholders’ equity	531,719	460,880
Total liabilities and shareholders' equity	745,709	676,286
Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	192,604	143,826	39,597	91,466
Accounts receivable, net	138,903	117,526
Intercompany balances	4,166	6,152
Inventories	82,457	85,483
Other current assets	(368)	(10,070)
Total current assets	417,762	342,917
Property, plant, and equipment, net	93,906	104,642
Goodwill	298,258	282,300
Acquired intangibles	97,171	101,520
Other assets	4,681	3,922
Investment in subsidiaries	61,746	58,477
Total assets	973,524	893,778
Current liabilities:
Accounts payable	77,786	66,363
Accrued expenses	67,746	60,004
Billings in Excess of Cost	9,840	9,301
Current maturities of long-term debt	400	400
Total current liabilities	155,772	136,068
Long-term debt	1,100	1,200
Deferred income taxes	28,907	35,354
Other non-current liabilities	47,775	58,038
Total shareholders’ equity	739,970	663,118
Total liabilities and shareholders' equity	973,524	893,778
Non-Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	29,676	26,351	29,261	19,144
Accounts receivable, net	6,482	6,546
Intercompany balances	(4,490)	(5,537)
Inventories	3,915	4,129
Other current assets	3,680	3,623
Total current assets	39,263	35,112
Property, plant, and equipment, net	3,192	3,662
Goodwill	22,816	21,732
Acquired intangibles	8,597	9,270
Other assets	0	0
Investment in subsidiaries	0	0
Total assets	73,868	69,776
Current liabilities:
Accounts payable	4,601	3,581
Accrued expenses	2,252	3,019
Billings in Excess of Cost	2,939	2,051
Current maturities of long-term debt	0	0
Total current liabilities	9,792	8,651
Long-term debt	0	0
Deferred income taxes	2,330	2,648
Other non-current liabilities	0	0
Total shareholders’ equity	61,746	58,477
Total liabilities and shareholders' equity	73,868	69,776
Eliminations
Current assets:
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	(801,716)	(721,595)
Total assets	(801,716)	(721,595)
Current liabilities:
Accounts payable	0	0
Accrued expenses	0	0
Billings in Excess of Cost	0	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	(801,716)	(721,595)
Total liabilities and shareholders' equity	$ (801,716)	$ (721,595)