Postretirement and Other Employee Benefits (Net Periodic Benefit Cost for Pension Plans) (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Postretirement and Other Employee Benefits [Abstract]
Service cost	$ 1,068	$ 883	$ 1,054
Interest cost	2,942	4,844	5,554
Expected long-term return on plan assets	(4,206)	(5,560)	(5,778)
Recognized actuarial loss	1,929	1,046	1,723
Net curtailment gain			(2,542)
Amortization of prior service credit	(138)	(139)	(147)
Net settlement loss	1,472
Net periodic benefit cost	$ 3,067	$ 1,074	$ (136)