Taxes [Line Items]

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- Definition

Unrecognized Tax Benefits, Income Tax Expense

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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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- Definition

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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- Definition

The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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- Definition

The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.

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- Definition

Amount of increase in unrecognized tax benefits resulting from settlements with taxing authorities.

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Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended			6 Months Ended
	Jul. 31, 2017	Apr. 30, 2020	Apr. 30, 2019	Jan. 31, 2019	Apr. 30, 2020	Nov. 01, 2018
Taxes [Line Items]
Statutory federal income tax rate					21.00%
Minimum
Taxes [Line Items]
Estimated potential decrease in underlying unrecognized tax benefits		$ 0			$ 0
Maximum
Taxes [Line Items]
Estimated potential decrease in underlying unrecognized tax benefits		62,000,000			$ 62,000,000
Retained Earnings \| Accounting Standards Update 2016-16
Taxes [Line Items]
Cumulative effect adjustment						$ 130,500,000
Synopsys Hungary \| Foreign Tax Authority \| Tax Year 2011 - Tax Year 2013 \| Hungarian Tax Authority
Taxes [Line Items]
Aggregate tax assessment	$ 25,000,000.0
Estimate of additional penalties and interest	$ 11,000,000.0
Unrecognized tax benefits			$ 17,400,000
Synopsys Hungary \| Foreign Tax Authority \| Tax Year 2014 - Tax Year 2018 \| Hungarian Tax Authority
Taxes [Line Items]
Unrecognized tax benefits from settlement with tax authorities		$ 6,900,000
Fiscal Year 2017 \| Taipei
Taxes [Line Items]
Unrecognized tax benefits from settlement with tax authorities				$ 5,500,000