Net Income per Share - Reconciliation of Weighted Average Common Shares Used to Calculate Basic Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020
Numerator:
Net income attributed to Synopsys		$ 198,646	$ 252,911	$ 556,069	$ 466,892
Denominator:
Weighted-average common shares for basic net income per share (shares)		152,635	151,352	152,619	150,731
Dilutive effect of potential common shares from equity-based compensation (shares)		4,272	4,621	4,539	4,343
Weighted-average common shares for diluted net income per share (shares)		156,907	155,973	157,158	155,074
Net income per share attributed to Synopsys:
Basic (in USD per share)		$ 1.30	$ 1.67	$ 3.64	$ 3.10
Diluted (in USD per share)		$ 1.27	$ 1.62	$ 3.54	$ 3.01
Anti-dilutive employee stock-based awards excluded (shares)	[1]	355	3	405	610

[1] These stock options and unvested restricted stock units were anti-dilutive for the respective periods and are excluded in calculating diluted net income per share. While such awards were anti-dilutive for the respective periods, they could be dilutive in the future.