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Segment Information (Details) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2018 USD ($) segment | Sep. 30, 2017 USD ($)
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |  |  |
Number of reportable segments | segment |  |  | 3 |
Net sales: | $ 280,086 | $ 274,574 | $ 761,459 | $ 728,806
Income from operations: | 70,279 | 68,735 | 189,100 | 179,815
Unallocated Corporate Expenses | (8,698) | (2,174) | (22,839) | (15,977)
Total income from operations | 29,404 | 35,693 | 75,521 | 70,302
Residential Products |  |  |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |  |  |
Net sales: | 125,839 | 129,501 | 360,915 | 361,304
Income from operations: | 20,138 | 23,764 | 57,572 | 61,984
Industrial and Infrastructure Products |  |  |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |  |  |
Net sales: | 55,761 | 56,938 | 171,357 | 164,812
Income from operations: | 2,892 | 2,554 | 12,098 | 5,914
Renewable Energy & Conservation |  |  |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |  |  |
Net sales: | 98,486 | 88,135 | 229,187 | 202,690
Income from operations: | 15,072 | 11,549 | 28,690 | 18,381
Intersegment Elimination |  |  |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |  |  |
Net sales: | (272) | (224) | (861) | (994)
Intersegment Elimination | Industrial and Infrastructure Products |  |  |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |  |  |
Net sales: | $ 56,033 | $ 57,162 | $ 172,218 | $ 165,806

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