Fair Value Measurements - Fair Value Measurements (Details) - USD ($) $ in Thousands	Nov. 30, 2016	Aug. 31, 2016
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	$ 48,986	$ 50,099
Embedded derivative asset	24,106
Other assets	13,303	12,678
Total assets	481,392	606,598
Foreign currency derivatives		22,289
Total liabilities	325,786	528,650
Fair Value, Measurements, Recurring [Member] | 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	48,986	50,099
Embedded derivative asset	0
Other assets	13,303	12,678
Total assets	93,834	125,315
Foreign currency derivatives		0
Total liabilities	22,444	22,331
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	0	0
Embedded derivative asset	24,106
Other assets	0	0
Total assets	387,558	481,283
Foreign currency derivatives		22,289
Total liabilities	295,061	491,268
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation assets	0	0
Embedded derivative asset	0
Other assets	0	0
Total assets	0	0
Foreign currency derivatives		0
Total liabilities	8,281	15,051
Commodity and freight derivatives | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	364,218	500,192
Derivative Liability	300,167	491,302
Commodity and freight derivatives | Fair Value, Measurements, Recurring [Member] | 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	31,545	62,538
Derivative Liability	22,444	22,331
Commodity and freight derivatives | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	332,673	437,654
Derivative Liability	277,723	468,971
Commodity and freight derivatives | Fair Value, Measurements, Recurring [Member] | 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, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives	20,335	21,551
Foreign currency derivatives	15,690
Foreign currency derivatives | Fair Value, Measurements, Recurring [Member] | 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 | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives	20,335	21,551
Foreign currency derivatives	15,690
Foreign currency derivatives | Fair Value, Measurements, Recurring [Member] | 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, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	10,444	22,078
Derivative Liability	1,648	8
Interest rate swap derivatives | Fair Value, Measurements, Recurring [Member] | 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	0
Derivative Liability	0	0
Interest rate swap derivatives | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	10,444	22,078
Derivative Liability	1,648	8
Interest rate swap derivatives | Fair Value, Measurements, Recurring [Member] | 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
NCRA [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Crack spread contingent consideration liability	8,281
NCRA [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Crack spread contingent consideration liability		15,051
NCRA [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Crack spread contingent consideration liability	0	0
NCRA [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Crack spread contingent consideration liability	0	0
NCRA [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Crack spread contingent consideration liability	$ 8,281	$ 15,051