Exit Activity Costs and Asset Impairments (Schedule Of Asset Impairment Charges Related To Restructuring Activities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment (recoveries) charges, net	$ 408	$ 1,344	$ (1,630)
Exit activity costs	10,144	3,475	7,125
Total exit activity costs & asset impairments	10,552	4,819	5,495
Corporate
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment (recoveries) charges, net	0	0	0
Exit activity costs	1,660	438	261
Total exit activity costs & asset impairments	1,660	438	261
Renewable Energy & Conservation | Operating Segments
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment (recoveries) charges, net	(9)	105	509
Exit activity costs	66	(33)	2,986
Total exit activity costs & asset impairments	57	72	3,495
Residential Products | Operating Segments
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment (recoveries) charges, net	417	1,586	345
Exit activity costs	3,440	1,321	1,058
Total exit activity costs & asset impairments	3,857	2,907	1,403
Industrial and Infrastructure Products | Operating Segments
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment (recoveries) charges, net	0	(347)	(2,484)
Exit activity costs	4,978	1,749	2,820
Total exit activity costs & asset impairments	$ 4,978	$ 1,402	$ 336