Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020
Income Statement [Abstract]
Revenues	$ 1,497.4	$ 1,496.0	$ 2,989.8	$ 3,109.0
Operating expenses	1,274.5	1,306.1	2,523.8	2,739.9
Selling, general and administrative expenses	161.9	119.4	284.5	237.0
Restructuring and related expenses	0.0	1.8	0.0	5.0
Amortization of intangible assets	10.7	12.5	21.5	25.1
Impairment loss	0.0	172.8	0.0	172.8
Operating profit (loss)	50.3	(116.7)	160.1	(70.8)
Income from unconsolidated affiliates	0.2	0.9	0.8	1.8
Interest expense	(7.8)	(10.5)	(16.3)	(20.7)
Income (loss) from continuing operations before income taxes	42.8	(126.2)	144.6	(89.7)
Income tax provision	(11.7)	(10.6)	(38.9)	(19.2)
Income (loss) from continuing operations	31.1	(136.8)	105.7	(108.9)
Income from discontinued operations, net of taxes	0.0	0.0	0.0	0.1
Net income (loss)	31.1	(136.8)	105.7	(108.8)
Other comprehensive income (loss)
Interest rate swaps	1.6	(8.7)	2.8	(9.9)
Foreign currency translation and other	1.2	(4.2)	5.2	(3.8)
Income tax (provision) benefit	(0.4)	2.4	(0.8)	2.7
Comprehensive income (loss)	$ 33.4	$ (147.3)	$ 112.9	$ (119.8)
Net income (loss) per common share — Basic
Income (loss) from continuing operations (in USD per share)	$ 0.46	$ (2.05)	$ 1.57	$ (1.63)
Income from discontinued operations (in USD per share)	0	0	0	0
Net income (loss) (in USD per share)	0.46	(2.05)	1.57	(1.63)
Net income (loss) per common share — Diluted
Income (loss) from continuing operations (in USD per share)	0.46	(2.05)	1.56	(1.63)
Income from discontinued operations (in USD per share)	0	0	0	0
Net income (loss) (in USD per share)	$ 0.46	$ (2.05)	$ 1.56	$ (1.63)
Weighted-average common and common equivalent shares outstanding
Basic (in shares)	67.3	66.9	67.2	66.9
Diluted (in shares)	67.8	66.9	67.7	66.9