Stockholders' Equity - Share Repurchases (Details) - USD ($)	3 Months Ended	12 Months Ended
	Oct. 31, 2019	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017	Mar. 31, 2017	Dec. 31, 2011
Stockholders' Equity Note [Abstract]
Share repurchase program, maximum amount authorized					$ 1,000,000,000.0	$ 500,000,000.0
Share repurchase program, remaining authorized amount	$ 407,400,000	$ 407,400,000
Share repurchase program, common stock repurchased (in shares)	512,000	537,000	0
Share repurchase program, common stock repurchased	$ 150,000,000.0	$ 156,100,000		$ 55,000,000.0
Share repurchase program, average purchase price (in dollars per share)	$ 292.7