Benefit Plans - Schedule of Amortization From Other Accumulated Comprehensive Income into Net Period Benefit Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, health care benefits annual rate of increase in the per capita cost	7.50%
Defined benefit plan, health care benefits annual rate of increase in the per capita cost trend rate		5.00%
Qualified Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of transition obligation
Amortization of prior service cost (benefit)		1,597
Amortization of net actuarial loss		22,516
Non-Qualified Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of transition obligation
Amortization of prior service cost (benefit)		(33)
Amortization of net actuarial loss		32
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of transition obligation		563
Amortization of prior service cost (benefit)		(17)
Amortization of net actuarial loss		1,152