Fair Value Measurements - Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	May 31, 2018	Aug. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	$ 38,765	$ 52,414
Deferred purchase price receivable	464,516	548,602
Embedded derivative asset	23,145	25,533
Other assets	16,783	14,846
Total assets	1,025,925	1,044,792
Foreign currency derivatives		19,931
Total liabilities	362,298	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	38,765	52,414
Deferred purchase price receivable	0	0
Embedded derivative asset	0	0
Other assets	16,783	14,846
Total assets	100,004	115,751
Foreign currency derivatives		0
Total liabilities	37,297	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	23,145	25,533
Other assets	0	0
Total assets	461,405	380,439
Foreign currency derivatives		19,931
Total liabilities	325,001	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	464,516	548,602
Embedded derivative asset	0	0
Other assets	0	0
Total assets	464,516	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	473,418	384,648
Derivative Liability	330,364	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	44,456	48,491
Derivative Liability	37,294	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	428,962	336,157
Derivative Liability	293,070	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	9,298	8,771
Foreign currency derivatives	23,084
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	9,298	8,771
Foreign currency derivatives	23,084
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	8,850	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	3	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	8,847	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