Accumulated Other Comprehensive Income - Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Accumulated other comprehensive income
Selling, general and administrative expenses	$ (49,364)	$ (48,707)	$ (47,703)
Amortization of prior pension service costs and unrecognized losses	3	3	3
Settlement and curtailment loss	(155)	(511)
Tax expense (benefit)	(11,163)	(10,842)	(13,822)
Net income (loss)	34,157	32,711	$ 43,143
Reclassification out of accumulated other comprehensive income (loss)
Accumulated other comprehensive income
Net income (loss)	592	732
Restricted investments | Reclassification out of accumulated other comprehensive income (loss)
Accumulated other comprehensive income
Selling, general and administrative expenses	(37)	(11)
Tax expense (benefit)	9	3
Net income (loss)	(28)	(8)
Change in funded status of pension plans | Reclassification out of accumulated other comprehensive income (loss)
Accumulated other comprehensive income
Tax expense (benefit)	(202)	(246)
Net income (loss)	620	740
Change in funded status of pension plans | Reclassification out of accumulated other comprehensive income (loss) | Other income (expense)
Accumulated other comprehensive income
Amortization of prior pension service costs and unrecognized losses	667	475
Settlement and curtailment loss	$ 155	$ 511