GOODWILL AND RELATED INTANGIBLE ASSETS

Goodwill

The changes in the carrying amount of goodwill for the nine months ended September 30, 2018 are as follows (in thousands):



	Residential Products		Industrial and Infrastructure Products			Renewable Energy & Conservation			Total
Balance at December 31, 2017	$	198,075	$	54,280		$	68,719		$	321,074
Acquired goodwill	—		—			2,838			2,838
Adjustments to prior year acquisitions	—		(38		)	—			(38		)
Foreign currency translation	—		(165		)	(388		)	(553		)
Balance at September 30, 2018	$	198,075	$	54,077		$	71,169		$	323,321

Acquired Intangible Assets

Acquired intangible assets consist of the following (in thousands):



	September 30, 2018				December 31, 2017
	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization		Estimated Life
Indefinite-lived intangible assets:
Trademarks	$	45,096	$	—	$	45,107	$	—	Indefinite
Finite-lived intangible assets:
Trademarks	6,148		3,397		5,876		3,062		3 to 15 Years
Unpatented technology	28,644		13,406		28,107		12,033		5 to 20 Years
Customer relationships	70,593		34,626		80,707		39,652		5 to 17 Years
Non-compete agreements	1,649		1,156		1,649		931		4 to 10 Years
	107,034		52,585		116,339		55,678
Total acquired intangible assets	$	152,130	$	52,585	$	161,446	$	55,678

The Company recognized impairment charges related to a finite-lived intangible asset for the three and nine months ended September 30, 2018 of $1.3 million. The charge relates to the discontinuation of lower margin sales in the Residential Products segment.

The following table summarizes the acquired intangible asset amortization expense for the three and nine months ended September 30 (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Amortization expense	$	2,121	$	2,208	$	6,408	$	6,600

Amortization expense related to acquired intangible assets for the remainder of fiscal 2018 and the next five years thereafter is estimated as follows (in thousands):



	2018		2019		2020		2021		2022		2023
Amortization expense	$	1,960	$	7,841	$	7,329	$	6,726	$	6,315	$	5,776