Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Earnings Per Share [Abstract]
Options excluded from the diluted net earnings per share calculation (in shares)									0.8	0.1	1.0
Net earnings for basic and diluted earnings per share computation	$ 58.0	$ 75.2	$ 60.1	$ 73.8	$ 102.4	$ 69.9	$ (52.9)	$ 60.9	$ 267.2	$ 180.3	$ 232.8
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average common shares – basic									128.3	130.3	132.6
Dilutive impact of share-based awards									2.0	1.9	1.5
Weighted average common shares – diluted									130.3	132.2	134.1
Net earnings per share:
Net earnings per share – basic (in dollars per share)	$ 0.45	$ 0.59	$ 0.47	$ 0.57	$ 0.79	$ 0.54	$ (0.40)	$ 0.47	$ 2.08	$ 1.38	$ 1.76
Net earnings per share – diluted (in dollars per share)	$ 0.45	$ 0.58	$ 0.46	$ 0.56	$ 0.78	$ 0.53	$ (0.40)	$ 0.46	$ 2.05	$ 1.36	$ 1.74