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Summary of Significant Accounting Policies - Changes in Product Warranty Accrual (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Apr. 01, 2017
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]    
Warranty accrual, beginning of period $ 1,149 $ 910
Accrual for warranties issued 430 334
Changes to pre-existing warranties (including changes in estimates) (278) 61
Settlements made (161) (320)
Warranty accrual, end of period $ 1,140 $ 985