Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	May 31, 2019	Jan. 31, 2019	Jan. 31, 2018	Apr. 30, 2019	Apr. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)				14,000,000
Stock repurchased during the period (in shares)				2,100,000
Stock repurchased during the period				$ 104.4	$ 107.7
Shares with remaining authorization for repurchase under stock repurchase plan (in shares)				2,400,000
Cash dividend declared per common share (in usd per share)		$ 0.38	$ 0.36
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)	13,000,000
Cash dividend declared per common share (in usd per share)	$ 0.210