6.	Goodwill and Intangible Assets

Intangible Assets Subject to Amortization

Amortization of intangible assets other than goodwill is recognized on a straight-line basis over the estimated useful life of the intangible assets, except for customer relationships, which are recognized in proportion to the related projected revenue streams. Intangible assets with definite lives are reviewed for impairment if indicators of impairment arise. GSE does not have any intangible assets with indefinite useful lives other than goodwill.

During the three months ended March 31, 2020, we determined the impact of the COVID-19 virus on our operations was an indicator of a triggering event that could result in an impairment of our long-lived assets. As such, we performed an interim analysis to determine if an impairment existed at March 31, 2020 by its individual asset groupings, which management determined to be at the subsidiary level. We used a discounted cash flow analysis to test for impairment and concluded that the carrying value of the definite-lived intangible assets of DP Engineering exceeded its carrying value by $4.3 million, and we recorded an impairment for this amount as of March 31, 2020. No impairment was identified related to any other asset groupings.

Changes in the gross carrying amount, accumulated amortization, addition and impairment of definite-lived intangible assets was as follows:


(in thousands)	As of March 31, 2020
	Gross Carrying Amount		Accumulated Amortization			Impact of Impairment			Net
Amortized intangible assets:
Customer relationships	$	11,730	$	(4,584	)	$	(3,102	)	$	4,044
Trade names		2,467		(816	)		(778	)		873
Developed technology		471		(471	)		-			-
Non-contractual customer relationships		433		(433	)		-			-
Noncompete agreement		949		(267	)		(422	)		260
Alliance agreement		527		(198	)		-			329
Others		167		(167	)		-			-
Total	$	16,744	$	(6,936	)	$	(4,302	)	$	5,506

(in thousands)	As of December 31, 2019
	Gross Carrying Amount		Accumulated Amortization			Net
Amortized intangible assets:
Customer relationships	$	11,730	$	(4,079	)	$	7,651
Trade names		2,467		(727	)		1,740
Developed technology		471		(471	)		-
Non-contractual customer relationships		433		(433	)		-
Noncompete agreements		949		(217	)		732
Alliance agreement		527		(171	)		356
Others		167		(167	)		-
Total	$	16,744	$	(6,265	)	$	10,479

Amortization expense related to definite-lived intangible assets totaled $670 thousand and $570 thousand for the three months ended March 31, 2020 and 2019, respectively. The following table shows the estimated amortization expense of the definite-lived intangible assets for the next five years and thereafter:

(in thousands)
Years ended December 31:
2020 (remainder)	$	1,271
2021		1,213
2022		910
2023		640
2024		444
Thereafter		1,028
Total	$	5,506

Goodwill

We review goodwill for impairment annually as of December 31 and whenever events or changes in circumstances indicate the carrying value of goodwill may not be recoverable. We test goodwill at the reporting unit level. A reporting unit is an operating segment, or one level below an operating segment, as defined by U.S. GAAP. We have determined that we have two reporting units, which are the same as our two operating segments: (i) Performance Improvement Solutions ("Performance") and (ii) Nuclear Industry Training and Consulting ("NITC").

We reviewed our goodwill for impairment, due to the COVID-19 interim triggering event noted above. Based upon our analysis, we determined the fair value of our goodwill at the reporting unit level exceeded the carrying value and determined no impairment charge was required during the three months ended March 31, 2020.