Benefit Plans - Schedule of Amortization From Other Accumulated Comprehensive Income into Net Period Benefit Costs (Details) $ in Thousands	Aug. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, health care benefits annual rate of increase in the per capita cost	7.90%
Defined benefit plan, health care benefits, decrease in the per capita cost trend rate	4.50%
Qualified Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2018 Amortization of prior service cost (benefit)	$ 1,540
Fiscal 2018 Amortization of net actuarial (gain) loss	18,073
Non-Qualified Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2018 Amortization of prior service cost (benefit)	30
Fiscal 2018 Amortization of net actuarial (gain) loss	61
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Fiscal 2018 Amortization of prior service cost (benefit)	(565)
Fiscal 2018 Amortization of net actuarial (gain) loss	$ (1,224)