Derivative Financial Instruments and Hedging Activities - Derivatives (Details) $ in Thousands, bbl in Millions	9 Months Ended		12 Months Ended
	May 31, 2020 USD ($) bbl	May 31, 2019 USD ($)	Aug. 31, 2019 USD ($) bbl
Derivative [Line Items]
Derivative Liability, Noncurrent	$ 9,000		$ 7,400
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	349,372		180,894
Derivative Assets	409,662		246,728
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	60,290		65,834
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	266,693		191,073
Derivative Liabilities	375,467		244,019
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	1,487		4,191
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	107,287		48,755
Embedded Derivative, Gain on Embedded Derivative	$ 2,300	$ 2,400
Credit Rating Agencies Threshold, Minimum	66.67%
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	$ 16,400
Derivative Asset, Noncurrent, Excluding Fair Value Hedges	25,300		26,600
CF Nitrogen LLC [Member]
Derivative [Line Items]
Annual Payment Receivable Contingent On Investment Credit Rating	5,000
Embedded derivative asset	18,600
Foreign exchange derivatives | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	2,100		3,226
Derivative Assets	13,828		10,334
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	11,728		7,108
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	81,234		13,501
Derivative Liabilities	92,962		20,609
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0		0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	11,728		7,108
Derivative, Notional Amount	1,500,000		894,700
Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	18,636		21,364
Derivative Assets	18,636		21,364
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	0		0
Commodity derivatives | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	328,636		156,304
Derivative Assets	377,198		215,030
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	48,562		58,726
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	185,459		177,572
Derivative Liabilities	282,505		223,410
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	1,487		4,191
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	95,559		$ 41,647
Fair Value Hedging | Interest rate swap derivatives | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Notional Amount	$ 365,000
Cash Flow Hedging
Derivative [Line Items]
Aggregate notional amount of cash flow hedges (in barrels) | bbl	10.0		7.7
Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	$ 39,620		$ 33,179
Derivative Liabilities	$ 15,945		$ 5,351