Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended	12 Months Ended
	May 31, 2018	Aug. 31, 2017	Jun. 05, 2018
Equity, Class of Treasury Stock [Line Items]
Shares repurchase authorized amount		$ 160.0
Shares acquired through stock repurchase program (in shares)	4.3	6.7
Purchase of treasury stock	$ 109.1	$ 172.9
Weighted-average price per share (usd per share)	$ 25.23	$ 25.71
Remaining amount authorized for repurchase through share repurchase program	$ 50.9
Repurchase Program Through August 31, 2021 [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchase authorized amount			$ 500.0
Remaining amount authorized for repurchase through share repurchase program			$ 390.9