Derivative Financial Instruments and Hedging Activities Derivatives (Details) - USD ($)	3 Months Ended
	Nov. 30, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2016
Purchase and Sales Contracts [Line Items]
Credit Rating Agencies Threshold, Minimum	66.67%
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 389,329,000			$ 510,945,000
Derivative Asset, Fair Value, Gross Asset	419,103,000			543,821,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	29,774,000			32,876,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	287,494,000			479,912,000
Derivative Liability, Fair Value, Gross Liability	317,505,000			513,599,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	237,000			811,000
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	29,774,000			32,876,000
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	0
CF Nitrogen LLC [Member]
Purchase and Sales Contracts [Line Items]
Annual Payment Receivable Contingent On Investment Credit Rating	5,000,000
Payments For Credit Rating Decrease In Investment	5,000,000
Embedded derivative asset	24,100,000
Gain (Loss) on Investments	5,000,000
Embedded Derivative, Gain on Embedded Derivative	24,100,000
Foreign currency derivatives | Not Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	15,065,000			12,364,000
Derivative Asset, Fair Value, Gross Asset	20,335,000			21,551,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	5,270,000			9,187,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	10,420,000			13,102,000
Derivative Liability, Fair Value, Gross Liability	15,690,000			22,289,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0			0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	5,270,000			9,187,000
Derivative Asset, Notional Amount	789,100,000			802,200,000
Interest rate swap derivatives | Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	10,444,000			22,078,000
Derivative Asset, Fair Value, Gross Asset	10,444,000			22,078,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	0			0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	1,642,000
Derivative Liability, Fair Value, Gross Liability	1,642,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	0
Interest rate swap derivatives | Not Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	6,000			8,000
Derivative Liability, Fair Value, Gross Liability	6,000			8,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0			0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	0			0
Embedded Derivative Financial Instruments [Member] | Not Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	24,106,000
Derivative Asset, Fair Value, Gross Asset	24,106,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	0
Commodity and freight derivatives | Not Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	339,714,000			476,503,000
Derivative Asset, Fair Value, Gross Asset	364,218,000			500,192,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	24,504,000			23,689,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	275,426,000			466,802,000
Derivative Liability, Fair Value, Gross Liability	300,167,000			491,302,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	237,000			811,000
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	24,504,000			23,689,000
Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Increase (Decrease) in Fair Value of Hedged Item in Interest Rate Fair Value Hedge	13,300,000		$ 2,300,000
Fair Value Hedging [Member] | Interest rate swap derivatives | Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Notional Amount	495,000,000
Cash Flow Hedging [Member] | Interest rate swap derivatives | Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Notional Amount				$ 300,000,000
Cash paid to settle derivative	$ 5,100,000	$ 5,300,000	$ 6,400,000
Derivatives settled, number	2	2	2