Selected Quarterly Financial Data (Unaudited) - Financial Information (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 1,648.0	$ 1,647.9	$ 1,594.7	$ 1,607.9	$ 1,648.8	$ 1,624.3	$ 1,580.8	$ 1,588.3	$ 6,498.6	$ 6,442.2	$ 5,453.6
Gross profit	194.7	193.9	180.5	162.0	183.1	177.6	175.0	159.0
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
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 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 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