Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2021

Goodwill And Intangible Assets Disclosure [Abstract]

Reconciliation of Intangible Assets

The reconciliation of intangible assets for the nine months ended September 30, 2021 and 2020 was as follows (in thousands):

	September 30,			September 30,
	2021			2020
Patented technologies
Gross carrying amount at beginning of period	$	68,322		$	68,322
Gross carrying amount at end of period		68,322			68,322
Accumulated amortization at beginning of period		(43,113	)		(40,653	)
Amortization expense		(1,845	)		(1,845	)
Accumulated amortization at end of period		(44,958	)		(42,498	)
Net book value at end of period	$	23,364		$	25,824