Financial Assets and Liabilities - Summary of Cash Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Oct. 31, 2017	Oct. 31, 2016
Cash Equivalents
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost	$ 560,594	$ 504,972
Gross Unrealized Gains	0	0
Gross Unrealized Losses Less than 12 Months	0	0
Gross Unrealized Losses 12 Months or Longer	0	0
Estimated Fair Value	560,594	504,972
Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		140,676
Gross Unrealized Gains		60
Gross Unrealized Losses Less than 12 Months		(41)
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		140,695
Other Long-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Non-marketable equity securities, Cost	7,826	9,756
Gross Unrealized Gains	0	0
Gross Unrealized Losses Less Than 12Months	0	0
Gross Unrealized Loss Position 12Months Or Longer	0	0
Non-marketable equity securities	7,826	9,756
Money market funds \| Cash Equivalents
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost	560,594	499,274
Gross Unrealized Gains	0	0
Gross Unrealized Losses Less than 12 Months	0	0
Gross Unrealized Losses 12 Months or Longer	0	0
Estimated Fair Value	560,594	499,274
Commercial paper \| Cash Equivalents
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		1,498
Gross Unrealized Gains		0
Gross Unrealized Losses Less than 12 Months		0
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		1,498
Commercial paper \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		25,430
Gross Unrealized Gains		1
Gross Unrealized Losses Less than 12 Months		0
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		25,431
Certificates of deposit \| Cash Equivalents
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		4,200
Gross Unrealized Gains		0
Gross Unrealized Losses Less than 12 Months		0
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		4,200
Certificates of deposit \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		12,849
Gross Unrealized Gains		0
Gross Unrealized Losses Less than 12 Months		0
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		12,849
U.S. government agency securities \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		13,607
Gross Unrealized Gains		4
Gross Unrealized Losses Less than 12 Months		(8)
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		13,603
Corporate debt securities \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		58,753
Gross Unrealized Gains		43
Gross Unrealized Losses Less than 12 Months		(18)
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		58,778
Asset-backed securities \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		22,146
Gross Unrealized Gains		12
Gross Unrealized Losses Less than 12 Months		(12)
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		22,146
Non-U.S. government agency securities \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		3,403
Gross Unrealized Gains		0
Gross Unrealized Losses Less than 12 Months		(3)
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		3,400
Other \| Short-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, Cost		4,488
Gross Unrealized Gains		0
Gross Unrealized Losses Less than 12 Months		0
Gross Unrealized Losses 12 Months or Longer		0
Estimated Fair Value		4,488
Non-Marketable Equity Securities \| Other Long-term Investments
Cash, Cash Equivalents and Investments [Line Items]
Non-marketable equity securities, Cost	7,826	9,756
Gross Unrealized Gains	0	0
Gross Unrealized Losses Less Than 12Months	0	0
Gross Unrealized Loss Position 12Months Or Longer	0	0
Non-marketable equity securities	$ 7,826	$ 9,756

Cash, Cash Equivalents and Investments [Line Items]

No definition available.

Name:	snps_CashCashEquivalentsAndInvestmentsLineItems
Namespace Prefix:	snps_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Securities Owned Not Readily Marketable Accumulated Gross Unrealized Gain Before Tax

+ References

No definition available.

+ Details

Name:	snps_SecuritiesOwnedNotReadilyMarketableAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	snps_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Securities Owned Not Readily Marketable Continuous Unrealized Loss Position 12Months Or Longer Accumulated Loss

+ References

No definition available.

+ Details

Name:	snps_SecuritiesOwnedNotReadilyMarketableContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix:	snps_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Securities Owned Not Readily Marketable Continuous Unrealized Loss Position Less Than 12Months Accumulated Loss

+ References

No definition available.

+ Details

Name:	snps_SecuritiesOwnedNotReadilyMarketableContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix:	snps_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Securities Owned Not Readily Marketable, Cost

+ References

No definition available.

+ Details

Name:	snps_SecuritiesOwnedNotReadilyMarketableCost
Namespace Prefix:	snps_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

+ References

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Aggregate carrying value of owned private equity or other securities for which a quoted market price is not readily determinable, the value of which has been determined by management based upon fair value methods, including pricing of similar securities and valuation techniques and is included in the schedule of financial condition or the balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

+ Details

Name:	us-gaap_SecuritiesOwnedNotReadilyMarketable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_CashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_OtherLongTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=snps_OthersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=snps_NonMarketableEquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: