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Supplemental Financial Information (Schedule of Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Dec. 31, 2015
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Schedule Of Supplemental Financial Information [Line Items] |  |  |  |
Cash and cash equivalents | $ 208,032 | $ 170,177 | $ 173,062 | $ 68,858
Accounts receivable, net | 166,718 | 124,072 |  |
Intercompany balances | 0 | 0 |  |
Inventories | 85,156 | 89,612 |  |
Other current assets | 8,195 | 7,336 |  |
Total current assets | 468,101 | 391,197 |  |
Property, plant, and equipment, net | 94,488 | 108,304 |  |
Goodwill | 321,093 | 304,032 |  |
Acquired intangibles | 107,943 | 110,790 |  |
Other assets | 4,672 | 3,922 |  |
Investment in subsidiaries | 0 | 0 |  |
Total assets | 996,297 | 918,245 |  |
Accounts payable | 96,181 | 69,944 |  |
Accrued expenses | 83,264 | 70,392 |  |
Billings in excess of cost | 18,234 | 11,352 |  |
Current maturities of long-term debt | 400 | 400 |  |
Total current liabilities | 198,079 | 152,088 |  |
Long-term debt | 209,425 | 209,237 |  |
Deferred income taxes | 38,162 | 38,002 |  |
Other non-current liabilities | 45,200 | 58,038 |  |
Total shareholders’ equity | 505,431 | 460,880 |  |
Total liabilities and shareholders' equity | 996,297 | 918,245 |  |
Reportable Legal Entities | Guarantor Subsidiaries |  |  |  |
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |
Cash and cash equivalents | 182,827 | 143,826 | 149,784 | 39,597
Accounts receivable, net | 158,877 | 117,526 |  |
Intercompany balances | 21,351 | 6,152 |  |
Inventories | 80,771 | 85,483 |  |
Other current assets | (32) | (10,070) |  |
Total current assets | 443,794 | 342,917 |  |
Property, plant, and equipment, net | 90,933 | 104,642 |  |
Goodwill | 298,331 | 282,300 |  |
Acquired intangibles | 99,060 | 101,520 |  |
Other assets | 4,672 | 3,922 |  |
Investment in subsidiaries | 60,844 | 58,477 |  |
Total assets | 997,634 | 893,778 |  |
Accounts payable | 91,499 | 66,363 |  |
Accrued expenses | 79,332 | 60,004 |  |
Billings in excess of cost | 14,578 | 9,301 |  |
Current maturities of long-term debt | 400 | 400 |  |
Total current liabilities | 185,809 | 136,068 |  |
Long-term debt | 1,025 | 1,200 |  |
Deferred income taxes | 35,520 | 35,354 |  |
Other non-current liabilities | 45,200 | 58,038 |  |
Total shareholders’ equity | 730,080 | 663,118 |  |
Total liabilities and shareholders' equity | 997,634 | 893,778 |  |
Reportable Legal Entities | Non-Guarantor Subsidiaries |  |  |  |
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |
Cash and cash equivalents | 25,205 | 26,351 | 23,278 | 29,261
Accounts receivable, net | 7,841 | 6,546 |  |
Intercompany balances | (3,254) | (5,537) |  |
Inventories | 4,385 | 4,129 |  |
Other current assets | 4,191 | 3,623 |  |
Total current assets | 38,368 | 35,112 |  |
Property, plant, and equipment, net | 3,555 | 3,662 |  |
Goodwill | 22,762 | 21,732 |  |
Acquired intangibles | 8,883 | 9,270 |  |
Other assets | 0 | 0 |  |
Investment in subsidiaries | 0 | 0 |  |
Total assets | 73,568 | 69,776 |  |
Accounts payable | 4,682 | 3,581 |  |
Accrued expenses | 1,744 | 3,019 |  |
Billings in excess of cost | 3,656 | 2,051 |  |
Current maturities of long-term debt | 0 | 0 |  |
Total current liabilities | 10,082 | 8,651 |  |
Long-term debt | 0 | 0 |  |
Deferred income taxes | 2,642 | 2,648 |  |
Other non-current liabilities | 0 | 0 |  |
Total shareholders’ equity | 60,844 | 58,477 |  |
Total liabilities and shareholders' equity | 73,568 | 69,776 |  |
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 | (18,097) | (615) |  |
Inventories | 0 | 0 |  |
Other current assets | 4,036 | 13,783 |  |
Total current assets | (14,061) | 13,168 |  |
Property, plant, and equipment, net | 0 | 0 |  |
Goodwill | 0 | 0 |  |
Acquired intangibles | 0 | 0 |  |
Other assets | 0 | 0 |  |
Investment in subsidiaries | 730,080 | 663,118 |  |
Total assets | 716,019 | 676,286 |  |
Accounts payable | 0 | 0 |  |
Accrued expenses | 2,188 | 7,369 |  |
Billings in excess of cost | 0 | 0 |  |
Current maturities of long-term debt | 0 | 0 |  |
Total current liabilities | 2,188 | 7,369 |  |
Long-term debt | 208,400 | 208,037 |  |
Deferred income taxes | 0 | 0 |  |
Other non-current liabilities | 0 | 0 |  |
Total shareholders’ equity | 505,431 | 460,880 |  |
Total liabilities and shareholders' equity | 716,019 | 676,286 |  |
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 | (790,924) | (721,595) |  |
Total assets | (790,924) | (721,595) |  |
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 | (790,924) | (721,595) |  |
Total liabilities and shareholders' equity | $ (790,924) | $ (721,595) |  |

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