Income Taxes (Details) (USD $)	12 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2009
Income (loss) from continuing operations before income taxes [Abstract]
United States	$ 171,329,000	$ 117,104,000	$ (50,634,000)
Foreign	9,476,000	8,229,000	3,570,000
Income (loss) from continuing operations before income taxes	180,805,000	125,333,000	(47,064,000)
Current [Abstract]
Federal	33,499,000	25,187,000	(44,249,000)
State	2,583,000	1,801,000	(838,000)
Foreign	82,000	2,320,000	(134,000)
Total current	36,164,000	29,308,000	(45,221,000)
Deferred [Abstract]
Federal	19,164,000	10,466,000	25,536,000
State	383,000	812,000	(886,000)
Foreign	1,457,000	239,000	656,000
Total deferred	21,004,000	11,517,000	25,306,000
Income Tax Expense (Benefit)	57,168,000	40,825,000	(19,915,000)
Reconciliation of the difference between the federal statutory rate and the Company's effective tax rate [Abstract]
Federal statutory rate	35.00%	35.00%	(35.00%)
State taxes, net of credits	0.70%	0.70%	(8.70%)
Foreign income taxed at different rates	(0.60%)	(0.60%)	(1.40%)
Section 199 deduction	(1.00%)	(2.40%)	3.40%
Non-deductible officers’ compensation	0.30%	1.00%	(2.20%)
Noncontrolling interests	(1.00%)	(1.10%)	(0.60%)
Research and development credits	(0.50%)	0.00%	0.00%
Other	(1.30%)	0.00%	2.20%
Effective tax rate	31.60%	32.60%	(42.30%)
Deferred tax assets [Abstract]
Environmental liabilities	9,727,000	9,341,000
Employee benefit accruals	12,547,000	10,067,000
State income tax and other	2,948,000	3,297,000
Net operating loss carryforwards	988,000	1,107,000
State credit carryforwards	2,294,000	2,671,000
Inventory valuation methods	4,321,000	4,768,000
Alternative minimum tax credit carryforwards	0	742,000
Valuation allowance	(589,000)	(855,000)
Total deferred tax assets	32,236,000	31,138,000
Deferred tax liabilities [Abstract]
Accelerated depreciation and basis differences	101,457,000	77,457,000
Prepaid expense acceleration	2,287,000	2,064,000
Translation adjustment	2,086,000	1,210,000
Deferred Tax Liabilities	105,830,000	80,731,000
Net deferred tax liability	73,594,000	49,593,000
Unrecognized tax benefits, as of the beginning of the year	1,631,000	3,372,000	5,761,000
Additions for tax positions of prior years	0	0	201,000
Reductions for tax positions of prior years	(75,000)	(274,000)	(645,000)
Settlements with tax authorities	(875,000)	(315,000)	(1,159,000)
Additions for tax positions of the current year	160,000		657,000
Reductions for lapse of statutes	(538,000)	(1,152,000)	(1,443,000)
Unrecognized tax benefits, as of the end of the year	303,000	1,631,000	3,372,000
Deferred Tax Liabilities Correction [Member]
Reconciliation of the difference between the federal statutory rate and the Company's effective tax rate [Abstract]
Correction of error resulting in reduction of income tax expense	$ 3,000,000
Minimum [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Dates	2012
Maximum [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Dates	2029
PUERTO RICO
Reconciliation of the difference between the federal statutory rate and the Company's effective tax rate [Abstract]
Effective tax rate	7.00%