CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total
Balance at Aug. 31, 2018	$ 939	$ 13,104	$ (12,336)	$ 245,049	$ 246,756
Balance (in shares) at Aug. 31, 2018	9,396,947
Increase (Decrease) in Stockholders' Equity
Restricted stock grants, net of forfeitures	$ 1	(1)
Restricted stock grants, net of forfeitures (in shares)	9,308
Amortization of restricted stock grants		1,257			1,257
Amortization of stock option grants		375			375
Exercise of stock options	$ 1	301			302
Exercise of stock options (in shares)	7,022
Common stock received for payment of stock option exercises		(120)			(120)
Common stock received for payment of stock option exercises (in shares)	(954)
Cash dividend on common stock				(7,522)	(7,522)
Change in funded status of pension plans, net of tax			618		618
Foreign currency translation adjustment			(956)		(956)
Net unrealized gain (loss) on restricted investments, net of tax			(13)		(13)
Net income				22,637	22,637
Balance at May. 31, 2019	$ 941	14,916	(12,687)	260,186	263,356
Balance (in shares) at May. 31, 2019	9,412,323
Balance at Feb. 28, 2019	$ 941	14,328	(11,279)	251,645	255,635
Balance (in shares) at Feb. 28, 2019	9,412,323
Increase (Decrease) in Stockholders' Equity
Amortization of restricted stock grants		462			462
Amortization of stock option grants		126			126
Change in funded status of pension plans, net of tax			91		91
Foreign currency translation adjustment			(1,494)		(1,494)
Net unrealized gain (loss) on restricted investments, net of tax			(5)		(5)
Net income				8,541	8,541
Balance at May. 31, 2019	$ 941	14,916	(12,687)	260,186	263,356
Balance (in shares) at May. 31, 2019	9,412,323
Increase (Decrease) in Stockholders' Equity
Adoption of new accounting standard | ASU 2014-09				22	22
Balance at Aug. 31, 2019	$ 940	14,351	(14,324)	270,260	271,227
Balance (in shares) at Aug. 31, 2019	9,400,748
Increase (Decrease) in Stockholders' Equity
Restricted stock grants, net of forfeitures	$ 5	(5)
Restricted stock grants, net of forfeitures (in shares)	44,879
Amortization of restricted stock grants		1,686			1,686
Amortization of stock option grants		687			687
Exercise of stock options		123			123
Exercise of stock options (in shares)	3,618
Common stock received for payment of stock option exercises		(123)			(123)
Common stock received for payment of stock option exercises (in shares)	(1,057)
Common stock retained to pay statutory minimum withholding taxes on common stock		(484)			(484)
Common stock retained to pay statutory minimum withholding taxes on common stock (in shares)	(5,790)
Cash dividend on common stock				(7,539)	(7,539)
Change in funded status of pension plans, net of tax			444		444
Foreign currency translation adjustment			318		318
Net unrealized gain (loss) on restricted investments, net of tax			5		5
Net income				25,149	25,149
Balance at May. 31, 2020	$ 945	16,235	(14,945)	289,258	291,493
Balance (in shares) at May. 31, 2020	9,442,398
Balance at Feb. 29, 2020	$ 945	15,882	(14,060)	279,350	282,117
Balance (in shares) at Feb. 29, 2020	9,448,620
Increase (Decrease) in Stockholders' Equity
Restricted stock grants, net of forfeitures (in shares)	(432)
Amortization of restricted stock grants		606			606
Amortization of stock option grants		231			231
Common stock retained to pay statutory minimum withholding taxes on common stock		(484)			(484)
Common stock retained to pay statutory minimum withholding taxes on common stock (in shares)	(5,790)
Change in funded status of pension plans, net of tax			185		185
Foreign currency translation adjustment			(1,077)		(1,077)
Net unrealized gain (loss) on restricted investments, net of tax			7		7
Net income				9,908	9,908
Balance at May. 31, 2020	$ 945	$ 16,235	(14,945)	289,258	$ 291,493
Balance (in shares) at May. 31, 2020	9,442,398
Increase (Decrease) in Stockholders' Equity
Adoption of new accounting standard | ASU 2018-02			(1,388)	$ 1,388
Adoption of new accounting standard			$ (1,388)