Other Assets - Narrative (Details) - USD ($)	2 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Jul. 31, 2017	Aug. 31, 2017	May 31, 2017	May 31, 2017	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Goodwill [Line Items]
Goodwill		$ 154,055,000			$ 154,055,000	$ 160,414,000	$ 150,115,000
Goodwill, Acquired During Period						9,774,000
Amortization of intangible assets					4,300,000	6,100,000	7,300,000
Goodwill, Written off Related to Sale of Business Unit						(695,000)
Goodwill impairment, result of annual impairment analysis	$ 0			$ 0
Goodwill, Impairment Loss			$ (5,500,000)		(5,542,000)
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down		26,900,000	$ 51,800,000
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment		8,200,000			8,200,000
Disposal Group, Including Discontinued Operation, Inventory		20,500,000			20,500,000
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net		6,300,000			6,300,000
Foods [Member]
Goodwill [Line Items]
Goodwill		0			0
Nitrogen Production [Member]
Goodwill [Line Items]
Goodwill		0			0
Ag [Member]
Goodwill [Line Items]
Goodwill		$ 142,929,000			142,929,000	148,916,000	$ 142,665,000
Goodwill, Acquired During Period						5,726,000
Finite-lived intangible assets acquired					500,000	2,800,000
Goodwill, Written off Related to Sale of Business Unit						(695,000)
Goodwill, Impairment Loss					$ (5,542,000)
Minimum | Other Intangible Assets [Member]
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life					2 years
Minimum | Major Maintenance Activities Requiring Shutdown
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life					2 years
Maximum | Other Intangible Assets [Member]
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life					30 years
Maximum | Major Maintenance Activities Requiring Shutdown
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life					4 years
Cash Distribution [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Goodwill [Line Items]
Payments to Acquire Assets, Investing Activities						$ 11,900,000