Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Segment Reporting, Other Significant Reconciling Item [Line Items]
Number of reportable segments | segment			3
Net sales:	$ 274,574	$ 272,734	$ 728,806	$ 776,143
Income from operations:	68,735	67,887	179,815	190,880
Unallocated Corporate Expenses	(2,174)	(11,164)	(15,977)	(25,902)
Total income from operations	35,693	26,522	70,302	72,859
Residential Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	129,501	117,957	361,304	338,069
Income from operations:	23,764	19,407	61,984	52,363
Industrial and Infrastructure Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	57,162	73,193	165,806	234,590
Income from operations:	2,554	1,913	5,914	11,429
Renewable Energy & Conservation
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	88,135	82,008	202,690	204,648
Income from operations:	11,549	16,366	18,381	34,969
Intersegment Elimination
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	(224)	(424)	(994)	(1,164)
Intersegment Elimination | Industrial and Infrastructure Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:	$ 56,938	$ 72,769	$ 164,812	$ 233,426