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Supplemental Financial Information (Schedule of Consolidating Statements of Income) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |  |  |  |  |
Net sales: | $ 280,086 |  |  | $ 274,574 |  |  | $ 761,459 | $ 728,806
Cost of sales | 209,807 |  |  | 205,839 |  |  | 572,359 | 548,991
Gross profit | 70,279 |  |  | 68,735 |  |  | 189,100 | 179,815
Selling, general, and administrative expense | 40,875 |  |  | 33,042 |  |  | 113,579 | 109,513
Income from operations | 29,404 |  |  | 35,693 |  |  | 75,521 | 70,302
Interest expense (income) | 2,906 |  |  | 3,486 |  |  | 9,305 | 10,612
Other expense (income) | 522 |  |  | 404 |  |  | (50) | 811
Income before taxes | 25,976 |  |  | 31,803 |  |  | 66,266 | 58,879
Provision for income taxes | 6,473 |  |  | 11,184 |  |  | 15,574 | 21,090
Income from continuing operations | 19,503 |  |  | 20,619 |  |  | 50,692 | 37,789
Loss before taxes | 0 |  |  | 0 |  |  | 0 | (644)
Benefit of income taxes | 0 |  |  | 0 |  |  | 0 | (239)
Loss from discontinued operations | 0 |  |  | 0 |  |  | 0 | (405)
Equity in earnings from subsidiaries | 0 |  |  | 0 |  |  | 0 | 0
Net income | 19,503 | $ 22,837 | $ 8,352 | 20,619 | $ 12,769 | $ 3,996 | 50,692 | 37,384
Reportable Legal Entities | Guarantor Subsidiaries |  |  |  |  |  |  |  |
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |  |  |  |  |
Net sales: | 268,302 |  |  | 264,448 |  |  | 729,256 | 700,848
Cost of sales | 200,725 |  |  | 198,103 |  |  | 548,391 | 527,389
Gross profit | 67,577 |  |  | 66,345 |  |  | 180,865 | 173,459
Selling, general, and administrative expense | 39,466 |  |  | 31,003 |  |  | 108,639 | 101,190
Income from operations | 28,111 |  |  | 35,342 |  |  | 72,226 | 72,269
Interest expense (income) | (427) |  |  | 105 |  |  | (724) | 459
Other expense (income) | 95 |  |  | 100 |  |  | 234 | 345
Income before taxes | 28,443 |  |  | 35,137 |  |  | 72,716 | 71,465
Provision for income taxes | 7,182 |  |  | 12,219 |  |  | 17,391 | 24,957
Income from continuing operations |  |  |  |  |  |  |  | 46,508
Loss before taxes |  |  |  |  |  |  |  | (644)
Benefit of income taxes |  |  |  |  |  |  |  | (239)
Loss from discontinued operations |  |  |  |  |  |  |  | (405)
Equity in earnings from subsidiaries | 888 |  |  | 293 |  |  | 3,312 | (1,747)
Net income | 22,149 |  |  | 23,211 |  |  | 58,637 | 44,356
Reportable Legal Entities | Non-Guarantor Subsidiaries |  |  |  |  |  |  |  |
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |  |  |  |  |
Net sales: | 19,211 |  |  | 15,514 |  |  | 45,735 | 37,383
Cost of sales | 16,338 |  |  | 12,844 |  |  | 36,987 | 30,565
Gross profit | 2,873 |  |  | 2,670 |  |  | 8,748 | 6,818
Selling, general, and administrative expense | 1,374 |  |  | 2,005 |  |  | 4,825 | 8,212
Income from operations | 1,499 |  |  | 665 |  |  | 3,923 | (1,394)
Interest expense (income) | (70) |  |  | (21) |  |  | (178) | (54)
Other expense (income) | 427 |  |  | 304 |  |  | (284) | 466
Income before taxes | 1,142 |  |  | 382 |  |  | 4,385 | (1,806)
Provision for income taxes | 254 |  |  | 89 |  |  | 1,073 | (59)
Income from continuing operations |  |  |  |  |  |  |  | (1,747)
Loss before taxes |  |  |  |  |  |  |  | 0
Benefit of income taxes |  |  |  |  |  |  |  | 0
Loss from discontinued operations |  |  |  |  |  |  |  | 0
Equity in earnings from subsidiaries | 0 |  |  | 0 |  |  | 0 | 0
Net income | 888 |  |  | 293 |  |  | 3,312 | (1,747)
Reportable Legal Entities | Gibraltar Industries, Inc. |  |  |  |  |  |  |  |
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |  |  |  |  |
Net sales: | 0 |  |  | 0 |  |  | 0 | 0
Cost of sales | 0 |  |  | 0 |  |  | 0 | 0
Gross profit | 0 |  |  | 0 |  |  | 0 | 0
Selling, general, and administrative expense | 35 |  |  | 34 |  |  | 115 | 111
Income from operations | (35) |  |  | (34) |  |  | (115) | (111)
Interest expense (income) | 3,403 |  |  | 3,402 |  |  | 10,207 | 10,207
Other expense (income) | 0 |  |  | 0 |  |  | 0 | 0
Income before taxes | (3,438) |  |  | (3,436) |  |  | (10,322) | (10,318)
Provision for income taxes | (963) |  |  | (1,124) |  |  | (2,890) | (3,808)
Income from continuing operations |  |  |  |  |  |  |  | (6,510)
Loss before taxes |  |  |  |  |  |  |  | 0
Benefit of income taxes |  |  |  |  |  |  |  | 0
Loss from discontinued operations |  |  |  |  |  |  |  | 0
Equity in earnings from subsidiaries | 22,149 |  |  | 23,211 |  |  | 58,637 | 44,356
Net income | 19,674 |  |  | 20,899 |  |  | 51,205 | 37,846
Eliminations |  |  |  |  |  |  |  |
Schedule Of Supplemental Financial Information [Line Items] |  |  |  |  |  |  |  |
Net sales: | (7,427) |  |  | (5,388) |  |  | (13,532) | (9,425)
Cost of sales | (7,256) |  |  | (5,108) |  |  | (13,019) | (8,963)
Gross profit | (171) |  |  | (280) |  |  | (513) | (462)
Selling, general, and administrative expense | 0 |  |  | 0 |  |  | 0 | 0
Income from operations | (171) |  |  | (280) |  |  | (513) | (462)
Interest expense (income) | 0 |  |  | 0 |  |  | 0 | 0
Other expense (income) | 0 |  |  | 0 |  |  | 0 | 0
Income before taxes | (171) |  |  | (280) |  |  | (513) | (462)
Provision for income taxes | 0 |  |  | 0 |  |  | 0 | 0
Income from continuing operations |  |  |  |  |  |  |  | (462)
Loss before taxes |  |  |  |  |  |  |  | 0
Benefit of income taxes |  |  |  |  |  |  |  | 0
Loss from discontinued operations |  |  |  |  |  |  |  | 0
Equity in earnings from subsidiaries | (23,037) |  |  | (23,504) |  |  | (61,949) | (42,609)
Net income | $ (23,208) |  |  | $ (23,784) |  |  | $ (62,462) | $ (43,071)

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