Income Taxes Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	3 Months Ended		9 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate			25.70%	35.00%
State income taxes, net of federal tax benefit			3.40%	2.60%
Federal tax benefit of statutory tax deduction			(1.30%)	(1.40%)
Employment related and other tax credits, net			(1.50%)	(1.70%)
Stock option excess tax benefit			(2.80%)	(1.40%)
Deferred tax revaluation			(28.10%)	0.00%
Other			(0.10%)	0.40%
Effective tax rate	26.10%	34.00%	(4.70%)	33.50%