Marketable Securities (Details 1) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	May 31, 2017	Aug. 31, 2016
Net Investment Income [Line Items]
Amortized cost	$ 3,389	$ 2,684
Gross unrealized losses	(1)	1
Estimated fair value	3,388	2,685
Long-term [Member]
Net Investment Income [Line Items]
Amortized cost	1,409	530
Gross unrealized losses		1
Estimated fair value	1,409	531
Commercial bonds [Member] | Short-term: [Member]
Net Investment Income [Line Items]
Amortized cost	1,951	2,118
Gross unrealized losses	(1)
Estimated fair value	1,950	2,118
Accrued interest [Member] | Short-term: [Member]
Net Investment Income [Line Items]
Amortized cost	29	36
Gross unrealized losses
Estimated fair value	$ 29	$ 36