Business Combinations - Additional Information (Detail) $ in Thousands	12 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Business Acquisition [Line Items]
Number of businesses acquired	0	0
Goodwill	$ 800,890	$ 804,414	$ 798,415
QuadMetrics
Business Acquisition [Line Items]
Common stock acquired			100.00%
Cash consideration			$ 5,700
Intangible assets acquired			$ 2,000
Weighted average useful life			4 years
Goodwill			$ 3,900

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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.

+ References

No definition available.

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- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

The number of businesses acquired by the entity during the period.

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- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

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