Income Taxes (Provision For Income Taxes Computed By Applying The Statutory Federal Income Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Income Tax Disclosure [Abstract]
Amount computed by applying a tax rate of 35%	$ 33,413	$ 32,377	$ 32,103
State income taxes (net of federal income tax benefit)	2,489	2,553	1,330
Employment related and other tax credits, net	(1,834)	(2,324)	(2,096)
Change in uncertain tax positions	0	(3,027)	0
Federal tax benefit of statutory tax deduction	(1,560)	(1,279)	(4,093)
Other	(704)	137	(7)
Provision for income taxes	$ 31,804	$ 28,437	$ 27,237
Statutory federal income tax rate (percent)	35.00%	35.00%	35.00%