Derivative Financial Instruments and Hedging Activities Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Feb. 28, 2018	Aug. 31, 2017
Derivative [Line Items]
Derivative Asset, Noncurrent			$ 23,100	$ 186,900
Derivative Liability, Noncurrent			8,200	13,700
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			420,182	380,236
Derivative Assets			452,708	418,952
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet			32,526	38,716
Derivative Liability, Fair Value, Amount Not Offset Against Collateral			317,196	287,079
Derivative Liabilities			380,615	329,693
Derivative Liability, Collateral, Right to Reclaim Cash, Offset			30,893	3,898
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet			$ 32,526	38,716
Credit Rating Agencies Threshold, Minimum			66.67%
CF Nitrogen LLC [Member]
Derivative [Line Items]
Annual Payment Receivable Contingent On Investment Credit Rating			$ 5,000
Payments For Credit Rating Decrease In Investment	$ 5,000	$ 5,000
Embedded derivative asset			22,700
Embedded Derivative, Gain on Embedded Derivative		$ 24,100
Foreign currency derivatives | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			2,901	5,135
Derivative Assets			6,026	8,771
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet			3,125	3,636
Derivative Liability, Fair Value, Amount Not Offset Against Collateral			9,781	16,295
Derivative Liabilities			12,906	19,931
Derivative Liability, Collateral, Right to Reclaim Cash, Offset			0	0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet			3,125	3,636
Derivative Asset, Notional Amount			723,200	776,700
Interest rate swap derivatives | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral			1
Derivative Liabilities			1
Derivative Liability, Collateral, Right to Reclaim Cash, Offset			0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet			0
Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			22,704	25,533
Derivative Assets			22,704	25,533
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet			0	0
Commodity and freight derivatives | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			394,577	349,568
Derivative Assets			423,978	384,648
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet			29,401	35,080
Derivative Liability, Fair Value, Amount Not Offset Against Collateral			307,414	270,784
Derivative Liabilities			367,708	309,762
Derivative Liability, Collateral, Right to Reclaim Cash, Offset			30,893	3,898
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet			29,401	$ 35,080
Fair Value Hedging [Member] | Interest rate swap derivatives | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Notional Amount			$ 495,000