Fair Value Measurements - Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Feb. 28, 2018	Aug. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	$ 53,041	$ 52,414
Deferred purchase price receivable	517,759	548,602
Embedded derivative asset	22,704	25,533
Other assets	17,342	14,846
Total assets	1,040,850	1,044,792
Foreign currency derivatives		19,931
Total liabilities	389,231	330,400
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	53,041	52,414
Deferred purchase price receivable	0	0
Embedded derivative asset	0	0
Other assets	17,342	14,846
Total assets	96,385	115,751
Foreign currency derivatives		0
Total liabilities	55,696	31,189
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	0	0
Deferred purchase price receivable	0	0
Embedded derivative asset	22,704	25,533
Other assets	0	0
Total assets	426,706	380,439
Foreign currency derivatives		19,931
Total liabilities	333,535	299,211
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	0	0
Deferred purchase price receivable	517,759	548,602
Embedded derivative asset	0	0
Other assets	0	0
Total assets	517,759	548,602
Foreign currency derivatives		0
Total liabilities	0	0
Commodity and freight derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	423,978	384,648
Derivative Liability	367,708	309,762
Commodity and freight derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	26,002	48,491
Derivative Liability	55,696	31,189
Commodity and freight derivatives | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	397,976	336,157
Derivative Liability	312,012	278,573
Commodity and freight derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Derivative Liability	0	0
Foreign currency derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives	6,026	8,771
Foreign currency derivatives	12,906
Foreign currency derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives	0	0
Foreign currency derivatives	0
Foreign currency derivatives | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives	6,026	8,771
Foreign currency derivatives	12,906
Foreign currency derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives	0	0
Foreign currency derivatives	0
Interest rate swap derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		9,978
Derivative Liability	8,617	707
Interest rate swap derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Derivative Liability	0	0
Interest rate swap derivatives | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		9,978
Derivative Liability	8,617	707
Interest rate swap derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Derivative Liability	$ 0	$ 0