Exit Activity Costs and Asset Impairments (Summary Of Exit Activity Costs And Asset Impairments by Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment charges	$ (1,630)	$ 7,530	$ 8,504
Exit activity costs	7,125	6,217	1,418
Gain on sale leaseback			(6,799)
Total exit activity costs & asset impairments	5,495	13,747	3,123
Corporate
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment charges	0	0	0
Exit activity costs	261	58	0
Gain on sale leaseback			0
Total exit activity costs & asset impairments	261	58	0
Residential Products | Operating Segments
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment charges	345	1,459	6,495
Exit activity costs	1,058	1,074	1,256
Gain on sale leaseback			(6,799)
Total exit activity costs & asset impairments	1,403	2,533	952
Industrial and Infrastructure Products | Operating Segments
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment charges	(2,484)	4,221	2,009
Exit activity costs	2,820	4,546	162
Gain on sale leaseback			0
Total exit activity costs & asset impairments	336	8,767	2,171
Renewable Energy & Conservation | Operating Segments
Restructuring Cost and Reserve [Line Items]
Inventory write-downs &/or asset impairment charges	509	1,850	0
Exit activity costs	2,986	539	0
Gain on sale leaseback			0
Total exit activity costs & asset impairments	$ 3,495	$ 2,389	$ 0