Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Oct. 31, 2017	Dec. 11, 2017	Apr. 28, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Oct. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	SNPS
Entity Registrant Name	SYNOPSYS INC
Entity Central Index Key	0000883241
Current Fiscal Year End Date	--10-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		148,713,662
Entity Public Float			$ 8.0