Quarterly report pursuant to Section 13 or 15(d)

Changes in Initial Product Warranty Accrual and Expenses Under Initial and Extended Warranties (Detail)

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Changes in Initial Product Warranty Accrual and Expenses Under Initial and Extended Warranties (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Movement in Standard Product Warranty Accrual          
Initial warranty accrual, beginning balance $ 1,214 $ 1,460 $ 1,190 $ 1,706  
Provision for estimated warranty cost 378 25 624 2  
Warranty expenditures (233) (200) (455) (423)  
Initial warranty accrual, ending balance 1,359 1,285 1,359 1,285  
Less warranty accrual, long-term 221 296 221 296 $ 70
Total warranty accrual, current portion $ 1,138 $ 989 $ 1,138 $ 989 $ 1,120