Benefit Plans - Changes in Benefit Obligation and Plan (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Qualified Pension Benefits
Change in benefit obligation: [Rollforward]
Benefit obligation at beginning of period	$ 501,053	$ 493,601
Service cost	26,010	25,232	20,774
Interest cost	24,119	22,257	23,034
Transfers in from Agriliance Employees Retirement Plan	84,498
Actuarial loss (gain)	982	759
Defined benefit plan, benefit obligation, period increase (decrease)	62,755	(11,014)
Plan amendments		365
Defined benefit plan, gross prescription drug subsidy receipts received
Excise tax on high cost healthcare plans
Benefits Paid	(28,351)	(30,147)
Benefit obligation at end of period	671,066	501,053	493,601
Change in plan assets: [Abstract]
Fair value of plan assets at beginning of period	540,822	478,361
Actual gain on plan assets	50,515	57,608
Company contributions	28,000	35,000
Transfers in from Agriliance Employees Retirement Plan	97,210
Benefits Paid	(28,351)	(30,147)
Fair value of plan assets at end of period	688,196	540,822	478,361
Funded Status of Plan	17,130	39,769
Assets [Abstract]
Non-current assets	17,695	40,047
Liabilities [Abstract]
Current liabilities
Non-current liabilities	(565)	(278)
Ending balance	17,130	39,769
Amounts recognized in accumulated other comprehensive loss (pretax): [Abstract]
Net transition obligation
Prior service cost (credit)	9,392	11,223
Net loss	331,420	247,669
Noncontrolling interests		(20,524)
Ending balance	340,812	238,368
Non-Qualified Pension Benefits
Change in benefit obligation: [Rollforward]
Benefit obligation at beginning of period	29,728	47,233
Service cost	279	1,246	1,220
Interest cost	1,343	1,933	2,235
Actuarial loss (gain)	2,498	(1,233)
Defined benefit plan, benefit obligation, period increase (decrease)	1,956	(514)
Plan amendments		1,047
Defined benefit plan, gross prescription drug subsidy receipts received
Excise tax on high cost healthcare plans
Benefits Paid	(1,334)	(19,984)
Benefit obligation at end of period	34,470	29,728	47,233
Change in plan assets: [Abstract]
Fair value of plan assets at beginning of period	0	0
Actual gain on plan assets
Company contributions	1,334	19,984
Benefits Paid	(1,334)	(19,984)
Fair value of plan assets at end of period	0	0	0
Funded Status of Plan	(34,470)	(29,728)
Assets [Abstract]
Non-current assets
Liabilities [Abstract]
Current liabilities	(3,325)	(3,205)
Non-current liabilities	(31,145)	(26,523)
Ending balance	(34,470)	(29,728)
Amounts recognized in accumulated other comprehensive loss (pretax): [Abstract]
Net transition obligation
Prior service cost (credit)	1,316	497
Net loss	10,104	7,124
Noncontrolling interests		(82)
Ending balance	11,420	7,539
Other Benefits
Change in benefit obligation: [Rollforward]
Benefit obligation at beginning of period	56,864	46,262
Service cost	2,556	1,771	1,385
Interest cost	2,638	2,194	2,153
Actuarial loss (gain)	(1,997)	1,199
Defined benefit plan, benefit obligation, period increase (decrease)	6,437	912
Plan amendments	(899)
Defined benefit plan, gross prescription drug subsidy receipts received	625	216
Excise tax on high cost healthcare plans		6,279
Benefits Paid	(2,035)	(1,969)
Benefit obligation at end of period	64,189	56,864	46,262
Change in plan assets: [Abstract]
Fair value of plan assets at beginning of period	0	0
Actual gain on plan assets
Company contributions	2,035	1,969
Benefits Paid	(2,035)	(1,969)
Fair value of plan assets at end of period	0	0	0
Funded Status of Plan	(64,189)	(56,864)
Assets [Abstract]
Non-current assets
Liabilities [Abstract]
Current liabilities	(3,297)	(3,111)
Non-current liabilities	(60,892)	(53,753)
Ending balance	(64,189)	(56,864)
Amounts recognized in accumulated other comprehensive loss (pretax): [Abstract]
Net transition obligation	563	1,651
Prior service cost (credit)	(17)	(190)
Net loss	683	14,076
Noncontrolling interests		(3,821)
Ending balance	$ 1,229	$ 11,716