Net Income Per Common Share - Basic and Diluted Net Income Per Common Share Calculations (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income from continuing operations	$ 48.1	$ 36.5	$ 29.9	$ 13.0	$ 8.9	$ 33.7	$ 25.4	$ 28.0	$ 127.5	$ 95.9	$ 78.1
(Loss) income from discontinued operations, net of taxes	(0.1)	0.2	(0.2)	(0.1)	0.8	(0.1)	1.2	(0.1)	(0.1)	1.8	(74.3)
Net income	$ 47.9	$ 36.8	$ 29.7	$ 13.0	$ 9.7	$ 33.6	$ 26.6	$ 27.8	$ 127.4	$ 97.8	$ 3.8
Weighted-average common and common equivalent shares outstanding—Basic (in shares)									66.6	66.1	57.7
Effect of dilutive securities
Weighted-average common and common equivalent shares outstanding—Diluted (in shares)									66.9	66.4	58.3
Net income per common share — Basic
Income from continuing operations (usd per share)	$ 0.72	$ 0.55	$ 0.45	$ 0.20	$ 0.13	$ 0.51	$ 0.38	$ 0.42	$ 1.92	$ 1.45	$ 1.35
Income (Loss) from discontinued operations (usd per share)	0	0	0	0	0.01	0	0.02	0	0	0.03	(1.29)
Net income (usd per share)	0.72	0.55	0.45	0.20	0.15	0.51	0.40	0.42	1.91	1.48	0.07
Net income per common share — Diluted
Income from continuing operations (usd per share)	0.71	0.55	0.45	0.20	0.13	0.51	0.38	0.42	1.91	1.45	1.34
Income (Loss) from discontinued operations (usd per share)	0	0	0	0	0.01	0	0.02	0	0	0.03	(1.27)
Net income (usd per share)	$ 0.71	$ 0.55	$ 0.45	$ 0.19	$ 0.15	$ 0.51	$ 0.40	$ 0.42	$ 1.90	$ 1.47	$ 0.07
RSUs
Effect of dilutive securities
Effect of dilutive securities (in shares)									0.2	0.1	0.3
Stock options
Effect of dilutive securities
Effect of dilutive securities (in shares)									0.1	0.1	0.2
Performance shares
Effect of dilutive securities
Effect of dilutive securities (in shares)									0.1	0.0	0.1