Summary of Significant Accounting Policies - Derivative Assets and Liabilities Not Designated As Hedging Instruments (Details) (USD $)	3 Months Ended
	Nov. 30, 2013	Aug. 31, 2013	Nov. 30, 2012
Derivatives, Fair Value [Line Items]
Derivative Instruments, tax effect of unrealized gain or loss deferred into accumulated other comprehensive income	$ 7,200,000	$ 9,200,000
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	1,200,000
Derivative Asset, Fair Value, Gross Asset	390,084,000	499,890,000	635,684,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	268,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	42,186,000	54,067,000	46,579,000
Derivative Asset, Fair Value, Net	347,630,000	445,823,000	589,105,000
Derivative Liability, Fair Value, Gross Liability	407,238,000	465,066,000	525,094,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	7,374,000	1,591,000	10,087,000
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	42,186,000	54,067,000	46,579,000
Derivative Liability, Fair Value, Net	357,678,000	409,408,000	468,428,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	18,854,000	24,135,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet
Derivative Asset, Fair Value, Net	18,854,000	24,135,000
Interest Rate Swap [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		3,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet		3,000
Derivative Asset, Fair Value, Net
Derivative Liability, Fair Value, Gross Liability	245,000	248,000	483,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet		3,000
Derivative Liability, Fair Value, Net	245,000	245,000	483,000
Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6,776,000	7,079,000	3,140,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	1,060,000	957,000	1,000
Derivative Asset, Fair Value, Net	5,716,000	6,122,000	3,139,000
Derivative Liability, Fair Value, Gross Liability	1,647,000	5,925,000	6,234,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	1,060,000	957,000	1,000
Derivative Liability, Fair Value, Net	587,000	4,968,000	6,233,000
Commodity and Freight Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	364,454,000	468,673,000	632,544,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	268,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	41,126,000	53,107,000	46,578,000
Derivative Asset, Fair Value, Net	323,060,000	415,566,000	585,966,000
Derivative Liability, Fair Value, Gross Liability	405,346,000	458,893,000	518,377,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	7,374,000	1,591,000	10,087,000
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	41,126,000	53,107,000	46,578,000
Derivative Liability, Fair Value, Net	356,846,000	404,195,000	461,712,000
Immaterial Balance Sheet Revision [Member]
Derivatives, Fair Value [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	244,200,000
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	$ 11,663,000	$ 14,930,000