Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Accumulated other comprehensive income
Balance at the beginning of the period	$ (15,479)	$ (7,986)
Other comprehensive gains (losses) before reclassifications	1,164	(8,163)
Reclassifications to net income of previously deferred (gains) losses	846	670
Total other comprehensive income (loss)	2,010	(7,493)	$ (3,736)
Balance at the ending of the period	(13,469)	(15,479)	(7,986)
Restricted investments
Accumulated other comprehensive income
Balance at the beginning of the period	54	47
Other comprehensive gains (losses) before reclassifications	155	51
Reclassifications to net income of previously deferred (gains) losses	(88)	(44)
Total other comprehensive income (loss)	67	7
Balance at the ending of the period	121	54	47
Change in funded status of pension plan
Accumulated other comprehensive income
Balance at the beginning of the period	(7,336)	(5,934)
Other comprehensive gains (losses) before reclassifications	221	(2,116)
Reclassifications to net income of previously deferred (gains) losses	934	714
Total other comprehensive income (loss)	1,155	(1,402)
Balance at the ending of the period	(6,181)	(7,336)	(5,934)
Foreign currency translation adjustment
Accumulated other comprehensive income
Balance at the beginning of the period	(8,197)	(2,099)
Other comprehensive gains (losses) before reclassifications	788	(6,098)
Total other comprehensive income (loss)	788	(6,098)
Balance at the ending of the period	$ (7,409)	$ (8,197)	$ (2,099)