Derivative Financial Instruments and Hedging Activities Derivatives (Details) - USD ($)	3 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Aug. 31, 2017
Purchase and Sales Contracts [Line Items]
Derivative Asset, Noncurrent	$ 71,800,000		$ 196,900,000
Derivative Liability, Noncurrent	8,600,000		14,400,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	316,238,000		390,214,000
Derivative Asset, Fair Value, Gross Asset	355,031,000		428,930,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	38,793,000		38,716,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	185,702,000		287,786,000
Derivative Liability, Fair Value, Gross Liability	234,853,000		330,400,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	10,358,000		3,898,000
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	$ 38,793,000		38,716,000
Credit Rating Agencies Threshold, Minimum	66.67%
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	$ 5,000,000
Embedded derivative asset	22,300,000
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	1,556,000		5,135,000
Derivative Asset, Fair Value, Gross Asset	4,297,000		8,771,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	2,741,000		3,636,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	4,815,000		16,295,000
Derivative Liability, Fair Value, Gross Liability	7,556,000		19,931,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0		0
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	2,741,000		3,636,000
Derivative Asset, Notional Amount	646,300,000		776,700,000
Interest rate swap derivatives | Designated as Hedging Instrument [Member]
Purchase and Sales Contracts [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	3,596,000		9,978,000
Derivative Asset, Fair Value, Gross Asset	3,596,000		9,978,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	0		0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	2,641,000		707,000
Derivative Liability, Fair Value, Gross Liability	2,641,000		707,000
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	22,271,000		25,533,000
Derivative Asset, Fair Value, Gross Asset	22,271,000		25,533,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	0		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	288,815,000		349,568,000
Derivative Asset, Fair Value, Gross Asset	324,867,000		384,648,000
Derivative Asset, Fair Value, Gross Amount Not Offset on Balance Sheet	36,052,000		35,080,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	178,246,000		270,784,000
Derivative Liability, Fair Value, Gross Liability	224,656,000		309,762,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	10,358,000		3,898,000
Derivative Liability, Fair Value, Gross Amount Not Offset on Balance Sheet	36,052,000		$ 35,080,000
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	8,300,000	$ 13,300,000
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