Postretirement and Other Employee Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Postretirement and Other Employee Benefits [Abstract]
Service cost	$ 256	$ 314	$ 803	$ 935
Interest cost	1,384	1,726	4,267	5,094
Expected long-term return on plan assets	(1,440)	(1,562)	(4,431)	(4,600)
Recognized actuarial loss	479	666	1,491	1,975
Amortization of prior service cost	(35)	(62)	(114)	(185)
Net periodic benefit cost	$ 644	$ 1,082	$ 2,016	$ 3,219