Goodwill and Related Intangible Assets (Schedule of Impairment Charges) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Impairment of indefinite-lived intangibles	$ 247	$ 9,048	$ 4,863
Impairment of definite-lived intangibles	0	198	0
Residential Products
Finite-Lived Intangible Assets [Line Items]
Impairment of indefinite-lived intangibles	0	0	440
Impairment of definite-lived intangibles	0	0	0
Industrial and Infrastructure Products
Finite-Lived Intangible Assets [Line Items]
Impairment of indefinite-lived intangibles	0	7,980	4,423
Impairment of definite-lived intangibles	0	0	0
Renewable Energy & Conservation
Finite-Lived Intangible Assets [Line Items]
Impairment of indefinite-lived intangibles	247	1,068	0
Impairment of definite-lived intangibles	$ 0	$ 198	$ 0

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- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

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- Definition

Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

+ References

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