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 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Movement in Standard Product Warranty Accrual          
Initial warranty accrual, beginning balance $ 1,285 $ 1,919 $ 1,706 $ 2,188  
Provision for estimated warranty cost 190 282 192 379  
Warranty expenditures (325) (224) (748) (590)  
Initial warranty accrual, ending balance 1,150 1,977 1,150 1,977  
Less warranty accrual, long-term 107 955 107 955 $ 773
Total warranty accrual, current portion $ 1,043 $ 1,022 $ 1,043 $ 1,022 $ 933