Description of Business and Summary of Significant Accounting Policies (Details 1) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Maturity period of highly liquid instruments	90 days
Cash equivalents outstanding	$ 71.5	$ 22.4
Allowance for doubtful accounts	14.1	11.1
Net tax benefit (expense) of foreign currency translation adjustment component of accumulated other comprehensive income	0.0	0.0
Net tax benefit (expense) for unrealized gains on derivative instruments	(1.9)	(4.0)
Accumulated tax benefit (expense) on unrealized loss on derivative instruments	13.4	15.3
Net tax benefit (expense) of actuarial loss (gain) included in accumulated other comprehensive income	(1.0)	0.6
Net tax benefit (expense) of prior service cost included in accumulated other comprehensive income	(0.3)	(0.3)
Net tax benefit (expense) of available for sale securities component of AOCI	0.0	$ 0.0
Senior Non-Convertible Cumulative Preferred Stock	$ 49.8
Stock Options [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Common shares excluded from computation of diluted earnings per share			218
Stock Appreciation Rights [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Common shares excluded from computation of diluted earnings per share	265	2,381	3,585