Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended	12 Months Ended
	Feb. 28, 2017	Aug. 31, 2016	Oct. 31, 2016	May 31, 2016	Aug. 31, 2015
Equity [Abstract]
Shares repurchase authorized amount			$ 40.0	$ 155.0	$ 145.0
Shares acquired through stock repurchase program	3.7	5.2
Purchase of treasury stock	$ 97.5	$ 148.3
Weighted-average price per share	$ 26.21	$ 28.48
Remaining amount authorized for repurchase through share repurchase program	$ 75.4