Debt (Schedule Of Long-Term Debt) (Details) - USD ($) $ in Thousands	Aug. 31, 2017	Aug. 31, 2016
Debt Instrument [Line Items]
Total long-term debt	$ 637,521	$ 578,938
Less unamortized debt issuance costs	(9,405)	(11,334)
Less long-term debt due within one year	0	(1,417)
Long-term debt due after one year	628,116	566,187
Class A-2 2016 Fixed Rate Notes [Member]
Debt Instrument [Line Items]
Total long-term debt	422,521	423,938
Class A-1 2016 Fixed Rate Notes [Member]
Debt Instrument [Line Items]
Total long-term debt	60,000	0
Class A-2 2013 Fixed Rate Notes [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 155,000	$ 155,000