Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Movement in Standard Product Warranty Accrual      
Initial warranty accrual, beginning balance $ 1,706 $ 2,188 $ 1,449
Provision for estimated warranty cost 492 348 1,715
Warranty expenditures (1,008) (830) (976)
Initial warranty accrual, ending balance 1,190 1,706 2,188
Less warranty accrual, long-term 70 773 843
Total warranty accrual, current portion $ 1,120 $ 933 $ 1,345