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Product Warranties - Product Warranty Activity (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Guarantees [Abstract]      
Balance at the beginning of the period $ 372 $ 268 $ 290
Accruals for warranties for products sold in the period 366 250 173
Fulfillment of warranty obligations (398) (140) (117)
Revisions of estimated obligations (32) (6) (78)
Balance at the end of the period $ 308 $ 372 $ 268