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Intangible Assets - Schedule of Patent Cost and Other Asset (Detail) - Patents [Member] - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]    
Patent costs $ 1,859 $ 1,992
Accumulated amortization (1,434) (1,483)
Finite-lived intangible assets, net $ 425 $ 509