Intangible Assets

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

7. Intangible Assets

Intangible assets as of December 31, 2021 and 2020 are comprised of the following (in thousands):

	December 31, 2021
	Gross amount		Accumulated amortization			Net amount
Intellectual property assets	$	9,312	$	(6,935	)	$	2,377
Intangible assets	$	9,312	$	(6,935	)	$	2,377

	December 31, 2020
	Gross amount		Accumulated amortization			Net amount
Intellectual property assets	$	9,486	$	(6,759	)	$	2,727
Intangible assets	$	9,486	$	(6,759	)	$	2,727

Aggregate amortization expense for intangible assets totaled $744 thousand, $668 thousand and $598 thousand for the years ended December 31, 2021, 2020 and 2019, respectively.

The aggregate amortization expense of intangible assets for the next five years are estimated to be $704 thousand, $590 thousand, $438 thousand, $309 thousand and $196 thousand for the years ended December 31, 2022, 2023, 2024, 2025 and 2026, respectively.