Postretirement and Other Employee Benefits (Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Nov. 30, 2019	Nov. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 4,463	$ 295
Interest cost	763	885
Expected long-term return on plan assets	(2,786)	(1,352)
Recognized actuarial loss	223	208
Amortization of prior service credit	(11)	(12)
Net periodic benefit cost	$ 2,652	$ 24