Income Taxes (Schedule Of Effective income Tax Rate Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Aug. 31, 2014	Aug. 31, 2013	Aug. 31, 2012
Income Taxes [Abstract]
U.S statutory rate	$ 27,529	$ 37,558	$ 22,788
State and local taxes, net of federal tax benefit	1,067	1,365	1,337
Foreign tax rate differences	(116)	(103)	(338)
Domestic production activities deduction	(2,170)	(2,638)	(1,900)
Research and development and fuel tax credits	(89)	(289)	(105)
Other	922	844	49
Total income tax provision	$ 27,143	$ 36,737	$ 21,831
U.S statutory rate, percentage	35.00%	35.00%	35.00%
State and local taxes, net of federal tax benefit, percentage	1.40%	1.30%	2.00%
Foreign tax rate differences, percentage	(0.10%)	(0.10%)	(0.50%)
Domestic production activities deduction, percentage	(2.80%)	(2.50%)	(2.90%)
Research and development and fuel tax credits, percentage	(0.10%)	(0.30%)	(0.20%)
Other, percentage	1.10%	0.80%	0.10%
Effective rate, percentage	34.50%	34.20%	33.50%