Segment Information (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Segment Reporting, Other Significant Reconciling Item [Line Items]
Number of reportable segments \| segment	3
Net sales:	$ 227,417	$ 215,337
Income from operations:	43,900	48,318
Unallocated Corporate Expenses	(7,285)	(6,059)
Total income from operations	10,566	13,843
Residential Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	103,709	103,948
Income from operations:	12,090	13,238
Industrial and Infrastructure Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	54,871	54,403
Income from operations:	4,129	2,602
Renewable Energy & Conservation
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	68,837	56,986
Income from operations:	1,632	4,062
Operating Segments \| Residential Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	103,709	103,948
Operating Segments \| Industrial and Infrastructure Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	55,188	54,624
Intersegment Elimination
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	$ (317)	$ (221)

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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