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

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1,2)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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