Income Taxes Incomes Taxes (Details) $ in Millions, $ in Millions		3 Months Ended			9 Months Ended
	Jul. 06, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 CAD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Oct. 31, 2016 CAD ($)
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Percent		15.30%	40.90%
Income tax provision (benefit)		$ 12	$ (47)		$ 73	$ (55)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		83	(115)		406	(108)
Less: Net earnings attributable to noncontrolling interests		41	$ 19		92	54
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act 2017, Incomplete Accounting, Transition Tax Liability, adjustment		$ 12
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act 2017, Incomplete Accounting, Increase (Decrease) In Period, Percent		15.00%
Effective Income Tax Rate Excluding The Earnings Attributable To The Noncontrolling Interests		29.40%	35.20%
Prepaid income taxes		$ 17			17		$ 33
Canada Revenue Agency [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Estimate of Possible Loss		135		$ 174
Letter of Credit | Letter of Credit
Operating Loss Carryforwards [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding		$ 120			$ 120
Letter of Credit | Letter of Credit | Canada Revenue Agency [Member]
Operating Loss Carryforwards [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding								$ 67	$ 87
Operating equity method investments | Point Lisas Nitrogen Limited [Member] | The Board of Inland Revenue [Member]
Operating Loss Carryforwards [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions						$ 7
State and Local Jurisdiction [Member] | ILLINOIS
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 5