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Operating Segment, Geographic and Significant Customer Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 Segment Customer	Dec. 31, 2017 Customer	Dec. 31, 2016 Customer
Segment Reporting Information [Line Items]
Operating segments | Segment	4
Number of customer accounted for more than ten percent of consolidated revenue | Customer	0	1	1
Consolidated Revenue
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%
Semiconductor Test | Consolidated Revenue | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage	13.00%	22.00%	26.00%
Semiconductor Test | Customer 1 | Consolidated Revenue | Revenue from Rights Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage		13.00%	12.00%
Semiconductor Test | Customer 2 | Consolidated Revenue | Revenue from Rights Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, percentage			12.00%

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Number Of Customer Accounted For Ten Percent Or Greater Revenue

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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