Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Feb. 28, 2018	Feb. 28, 2018	Feb. 28, 2019	Sep. 01, 2018	Aug. 31, 2018
Basis Of Presentation [Line Items]
Retained earnings		$ 476,091	$ 476,091	$ 477,027		$ 484,886
ASC Topic 606 [Member]
Basis Of Presentation [Line Items]
Retained earnings					$ 485,418
ASU No. 2017-07 [Member]
Basis Of Presentation [Line Items]
Net periodic pension cost		$ 200	$ 200
ASU No. 2018-02 [Member]
Basis Of Presentation [Line Items]
Tax reclassification from accumulated other comprehensive income to retained earnings due to tax reform	$ 500
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | ASC Topic 606 [Member]
Basis Of Presentation [Line Items]
Retained earnings				$ (2,926)		$ 532