New Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Nov. 30, 2018	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017	Sep. 01, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings		$ 474,740	$ 484,886
Net periodic pension cost		445	449	$ 477
ASU 2016-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Right of use asset		25,600
Lease liability		29,400
ASC Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings					$ 485,418
ASC Topic 606 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings		$ (3,153)	532
ASU No. 2017-07 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net periodic pension cost			$ 400	$ 400
ASU No. 2018-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Tax reclassification from accumulated other comprehensive income to retained earnings due to tax reform	$ 500