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Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 2015 | Jan. 31, 2014 | Oct. 31, 2015
Taxes [Line Items] |  |  |
Statutory federal income tax rate | 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate |  |
Gross unrecognized tax benefits | $ 126.1 us-gaap_UnrecognizedTaxBenefits |  |
Unrecognized tax benefits that would affect effective tax rate | 122.5 us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate |  |
Estimated potential decrease in underlying unrecognized tax benefits, minimum | 0 us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeLowerBound |  |
Estimated potential decrease in underlying unrecognized tax benefits, maximum | 31 us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound |  |
IRS | Fiscal Year 2012 |  |  |
Taxes [Line Items] |  |  |
Unrecognized tax benefits decrease resulting from settlement |  | 10.0 us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember / snps_IncomeTaxExaminationByPeriodAxis = snps_FiscalYearTwentyTwelveMember |
Taiwan | Fiscal Year 2012 |  |  |
Taxes [Line Items] |  |  |
Unrecognized tax benefits decrease resulting from settlement | 1.1 us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities / us-gaap_IncomeTaxAuthorityAxis = country_TW / snps_IncomeTaxExaminationByPeriodAxis = snps_FiscalYearTwentyTwelveMember |  |
Forecast |  |  |
Taxes [Line Items] |  |  |
Expected research tax credit benefit |  |  | $ 12.4 snps_IncomeTaxRateReconciliationEstimatedResearchTaxCreditBenefitAmount / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember

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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 + Details
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- Definition Amount of (increase) decrease reasonably possible in the estimated lower bound of the unrecognized tax benefit for a tax position taken or expected to be taken. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount of (increase) decrease reasonably possible in the estimated upper bound of the unrecognized tax benefit for a tax position taken or expected to be taken. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Unrecognized Tax Benefit -URI http://asc.fasb.org/extlink&oid=6527854 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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