Stockholders' Equity - Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Apr. 30, 2021	Jan. 31, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020	Mar. 31, 2017	Dec. 31, 2011
Stockholders' Equity Note [Abstract]
Share repurchase program, authorized amount for repurchase						$ 1,000.0	$ 500.0
Treasury stock repurchase (in shares)	0			69,600	160,800
Treasury stock repurchase		$ 24.8	$ 47.8	$ 24.8	$ 47.8
Average repurchase price per share (in dollars per share)				$ 356.61	$ 296.88
Share repurchase program, remaining authorized amount for repurchase	$ 334.8			$ 334.8