The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Intangible Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Intangible Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets, gross	$ 2,867		$ 2,867		$ 2,867
Less: accumulated amortization	(2,803)		(2,803)		(2,765)
Intangible assets, net	64		64		102
Amortization expense	13	$ 13	38	$ 38
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2021	50		50
2022	50		50
Purchased technology-based intangible
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets, gross	2,358		2,358		2,358
Purchased patent
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets, gross	$ 509		$ 509		$ 509