Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2021

Goodwill And Intangible Assets Disclosure [Abstract]

Reconciliation of Intangible Assets

The reconciliation of intangible assets for the three months ended March 31, 2021 and 2020 was as follows (in thousands):

	March 31,			March 31,
	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		(615	)		(615	)
Accumulated amortization at end of period		(43,728	)		(41,268	)
Net book value at end of period	$	24,594		$	27,054