Restatement of Previously Issued Financial Information - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	May 31, 2019	May 31, 2018	Aug. 31, 2017	Aug. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to income before income taxes	$ 61,579			$ 236,839			$ 690,666	$ 422,898
Increase (decrease) to net income	(54,713)	$ (248,304)	$ (347,115)	(181,620)	$ (165,959)	$ (187,182)	(650,132)	(534,761)
Decrease in cash	(155,252)			(533,887)			(155,252)	(533,887)	$ (181,379)	$ (450,617)
Increase (decrease) to cost of goods sold	8,274,170			8,841,696			22,343,944	23,398,272
Increase (decrease) to income tax expense	6,866			55,219			40,534	(111,863)
Increase (decrease) to revenues	8,497,941			9,087,328			23,465,769	24,099,365
Decrease of inventory	$ (3,338,321)						$ (3,338,321)			$ (2,768,649)
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to income before income taxes				(52,645)				(51,592)
Increase (decrease) to net income				47,526				40,630
Increase (decrease) to cost of goods sold				112,447				224,116
Increase (decrease) to income tax expense				(5,119)				(10,962)
Increase (decrease) to revenues				59,803				171,857
Freight Derivatives And Related Misstatements [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Misstatement between line items in the Consolidated Statements of Cash Flows								3,000
Freight Derivatives And Related Misstatements [Member] | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to income before income taxes				(29,800)				(52,900)
Increase (decrease) to net income				24,700				48,500
Increase (decrease) to cost of goods sold				29,800				52,900
Increase (decrease) to income tax expense				(5,100)				(4,400)
Intercompany Misstatements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Misstatement between line items in the Consolidated Statements of Cash Flows								3,000
Intercompany Misstatements | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Misstatement between line items in the Consolidated Statements of Cash Flows									5,000
Other Misstatements | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to income before income taxes				(22,800)				1,300
Increase (decrease) to net income				22,800				(7,900)
Increase (decrease) to cost of goods sold				18,800
Increase (decrease) to income tax expense								(6,600)
Misstatement between line items in the Consolidated Statements of Cash Flows								18,300	49,200
Reduction of notes payable		$ 3,100
Other Misstatements, Excise Tax Credit [Member] | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to income before income taxes								1,300
Increase (decrease) to cost of goods sold								(13,700)
Other Misstatements, Valuation of Derivatives [Member] | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to cost of goods sold				$ 1,300				(6,600)
Other Misstatements, Postretirement Benefit Plan Activity | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to cost of goods sold								(2,600)
Other Misstatements, Timing Difference | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase (decrease) to cost of goods sold								$ 18,800
Decrease of inventory									24,100
Increase in accounts receivable									$ 24,100