Goodwill and Related Intangible Assets (Schedule of Changes in Carrying Amount of Goodwill) (Details) $ in Thousands	9 Months Ended
Sep. 30, 2019 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2018	$ 323,671
Acquired goodwill	4,185
Adjustments to prior year acquisitions	(172)
Foreign currency translation	299
Balance at September 30, 2019	327,983
Renewable Energy and Conservation
Goodwill [Roll Forward]
Balance at December 31, 2018	71,827
Acquired goodwill	4,185
Adjustments to prior year acquisitions	(172)
Foreign currency translation	137
Balance at September 30, 2019	75,977
Residential Products
Goodwill [Roll Forward]
Balance at December 31, 2018	198,075
Acquired goodwill	0
Foreign currency translation	0
Balance at September 30, 2019	198,075
Industrial and Infrastructure Products
Goodwill [Roll Forward]
Balance at December 31, 2018	53,769
Adjustments to prior year acquisitions	0
Foreign currency translation	162
Balance at September 30, 2019	$ 53,931

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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