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Segment Information (Details) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2018 USD ($) segment | Mar. 31, 2017 USD ($)
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |
Number of reportable segments | segment | 3 |
Net sales: | $ 215,337 | $ 206,605
Income from operations: | 48,318 | 49,255
Unallocated Corporate Expenses | (6,059) | (9,265)
Total income from operations | 13,843 | 9,679
Residential Products |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |
Net sales: | 103,948 | 104,551
Income from operations: | 13,238 | 15,641
Industrial and Infrastructure Products |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |
Net sales: | 54,624 | 50,718
Income from operations: | 2,602 | (37)
Renewable Energy & Conservation |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |
Net sales: | 56,986 | 51,792
Income from operations: | 4,062 | 3,340
Intersegment Elimination |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |
Net sales: | (221) | (456)
Intersegment Elimination | Industrial and Infrastructure Products |  |
Segment Reporting, Other Significant Reconciling Item [Line Items] |  |
Net sales: | $ 54,403 | $ 50,262

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