GOODWILL AND RELATED INTANGIBLE ASSETS

Goodwill

The changes in the carrying amount of goodwill for the years ended December 31 were as follows (in thousands):



	Residential Products		Industrial and Infrastructure Products			Renewable Energy and Conservation			Total
Balance at December 31, 2016	$	181,285	$	53,884		$	68,863		$	304,032
Acquired goodwill	16,790		—			—			16,790
Adjustments to prior year acquisitions	—		—			(832		)	(832		)
Foreign currency translation	—		396			688			1,084
Balance at December 31, 2017	$	198,075	$	54,280		$	68,719		$	321,074
Acquired goodwill	—		—			3,051			3,051
Adjustments to prior year acquisitions	—		(38		)	—			(38		)
Foreign currency translation	—		(473		)	57			(416		)
Balance at December 31, 2018	$	198,075	$	53,769		$	71,827		$	323,671

Goodwill is recognized net of accumulated impairment losses of $235.4 million as of December 31, 2018 and 2017, respectively. No goodwill impairment charges were recognized by the Company during 2018.

Annual Impairment Testing

The Company performed its annual goodwill impairment test as of October 31, 2018, 2017, and 2016. The Company did not recognize any impairment charges during 2018, 2017, and 2016 as a result of the annual goodwill impairment test. However, subsequent to the annual goodwill impairment test as of October 31, 2016, the Company discontinued its European residential solar racking business which resulted in an impairment charge against goodwill of $0.9 million which was recorded for the year ended December 31, 2016.

During the October 31, 2018 impairment test, the Company conducted a quantitative analysis for all twelve of the Company’s reporting units. The quantitative impairment test consists of comparing the fair value of a reporting unit with its carrying value including goodwill. The fair value of each reporting unit evaluated under the quantitative test was determined using two valuation techniques: an income approach and a market approach. Each valuation approach relies on significant assumptions including a weighted average cost of capital ("WACC") based upon the capital structure of market participants in the Company’s peer groups, projected revenue growth, forecasted cash flows, and earnings multiples based on the market value of the Company and market participants within its peer groups.

As a result of our annual testing for 2018 and 2017, none of the reporting units with goodwill as of our testing date had carrying values in excess of their fair values.

Interim Impairment Testing

We test goodwill and indefinite-lived intangible assets for impairment on an annual basis as of October 31 and at interim dates when indicators of impairment are present. In 2018, 2017 and 2016, no indicators of impairment were identified as of interim dates; therefore, no interim tests were performed.

Acquired Intangible Assets

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



	December 31, 2018				December 31, 2017
	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization		Estimated Useful Life
Indefinite-lived intangible assets:
Trademarks	$	43,870	$	—	$	45,107	$	—	Indefinite
Finite-lived intangible assets:
Trademarks	6,094		3,518		5,876		3,062		3 to 15 Years
Unpatented technology	28,644		13,881		28,107		12,033		5 to 20 Years
Customer relationships	70,419		35,678		80,707		39,652		5 to 17 Years
Non-compete agreements	1,649		1,224		1,649		931		4 to 10 Years
	106,806		54,301		116,339		55,678
Total acquired intangible assets	$	150,676	$	54,301	$	161,446	$	55,678

The Company recognized impairment charges related to indefinite-lived trademark intangible assets for the years ended December 31, 2018, 2017 and 2016. The Company also recognized impairment charges related to finite-lived intangible assets for the years ended December 31, 2018 and 2016.

The following table summarizes the impairment charges for the years ended December 31 (in thousands):



	2018				2017				2016
	Indefinite-lived intangibles (1)		Definite-lived intangibles (2)		Indefinite-lived intangibles (3)		Definite-lived intangibles		Indefinite-lived intangibles (4)		Definite-lived intangibles (5)
Residential Products	$	200	$	—	$	—	$	—	$	—	$	—
Industrial and Infrastructure Products	—		—		—		—		7,980		—
Renewable Energy and Conservation	1,037		315		247		—		1,068		198
Impairment charges	$	1,237	$	315	$	247	$	—	$	9,048	$	198

(1) Residential Products impairment charges due to annual testing. Renewable Energy and Conservation impairment charges due to the annual testing in its international solar racking business and restructuring in its domestic greenhouse business.

(2) Renewable Energy and Conservation impairment charges due to the restructuring in its domestic greenhouse business.

(3) Renewable Energy and Conservation impairment charges due to the discontinuation of its domestic greenhouse business in China.

(4) Industrial and Infrastructure Products impairment charges due to discontinuation of U.S. bar grating product line and annual testing. Renewable Energy and Conservation impairment due to discontinuation of European residential solar racking business and annual testing.

(5) Renewable Energy and Conservation impairment due to discontinuation of European residential solar racking business.

The Company recognized amortization expense related to the definite-lived intangible assets. The following table summarizes amortization expense for the years ended December 31 (in thousands):



	2018		2017		2016
Amortization expense	$	8,222	$	8,761	$	9,637

Amortization expense related to acquired intangible assets for the next five years ended December 31 is estimated as follows (in thousands):



	2019		2020		2021		2022		2023
Amortization expense	$	7,213	$	6,921	$	6,726	$	6,248	$	5,709