Fair Value Of Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	Feb. 28, 2017	Aug. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents carried at cost	$ 27.3	$ 59.2
2016 and 2013 Fixed Rate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, carrying value, including accrued interest	578.2	579.6
2016 and 2013 Fixed Rate Notes [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	578.2	579.6
2016 Variable Rate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, carrying value, including accrued interest	26.1	0.0
2016 Variable Rate Notes [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 26.1	$ 0.0