Intangible Assets

3 Months Ended

Mar. 31, 2021

Intangible Assets, Net (Excluding Goodwill) [Abstract]

Intangible Assets

10. INTANGIBLE ASSETS: 

Intangible assets consist of the following: 

	March 31, 2021							December 31, 2020
(In thousands)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Patents	$	1,866	$	(1,585	)	$	281	$	1,832	$	(1,542	)	$	290
Software	206		(206		)	—		206		(200		)	6
Marketing assets and customer relationships	86		(64		)	22		101		(72		)	29
Total intangible assets	$	2,158	$	(1,855	)	$	303	$	2,139	$	(1,814	)	$	325

Amortization expense in the three months ended March 31, 2021 and the three months ended March 31, 2020 was as follows:  

	Three Months Ended March 31,
(In thousands)	2021		2020
Patents	$	43	$	38
Software		6		8
Marketing assets and customer relationships		2		2
Total amortization expense	$	51	$	48

Estimated aggregate amortization expense based on current intangible assets for the next four years is expected to be as follows: $116,000 for the remainder of 2021; $113,000 in 2022; $64,000 in 2023; and $10,000 in 2024.