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

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Carrying value as of the balance sheet date of obligations incurred through that date and payable for estimated claims under standard and extended warranty protection rights granted to customers.

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Carrying value as of the balance sheet date of obligations incurred through that date and payable for estimated claims under standard and extended warranty protection rights granted to customers. For classified balance sheets, represents the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying value as of the balance sheet date of obligations incurred through that date and due after one year (or beyond the operating cycle if longer) for estimated claims under standard and extended warranty protection rights granted to customers.

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Amount of decrease in the standard and extended product warranty accrual from payments made in cash or in kind to satisfy claims under the terms of the standard and extended product warranty.

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Amount of increase (decrease) in the standard and extended product warranty accrual from changes in estimates attributable to preexisting product warranties.

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