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		6 Months Ended
		Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020
Numerator:
Net income attributed to Synopsys		$ 195,078	$ 109,920	$ 357,423	$ 213,981
Denominator:
Weighted-average common shares for basic net income per share (shares)		152,725	150,597	152,612	150,421
Dilutive effect of potential common shares from equity-based compensation (shares)		4,352	3,782	4,614	4,050
Weighted-average common shares for diluted net income per share (shares)		157,077	154,379	157,226	154,471
Net income per share attributed to Synopsys:
Basic (in USD per share)		$ 1.28	$ 0.73	$ 2.34	$ 1.42
Diluted (in USD per share)		$ 1.24	$ 0.71	$ 2.27	$ 1.39
Anti-dilutive employee stock-based awards excluded (shares)	[1]	466	743	415	579

[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.