CF Acquisition (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended					3 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Inventories At Price Tied To Natural Gas [Member] t	Sep. 30, 2014 Inventories At Price Tied To C F R Tampa Price [Member] t	Sep. 30, 2014 Plant City Trust [Member]	Dec. 31, 2014 Plant City Trust [Member] Estimate [Member]	Sep. 30, 2014 Bonnie Facility Trust [Member]	Dec. 31, 2015 Bonnie Facility Trust [Member] Estimate [Member]	Sep. 30, 2014 C F Florida Phosphates Assets [Member]	Sep. 30, 2014 C F Asset Retirement Obligations [Member]
Business Acquisition [Line Items]
Effective date of acquisition	Mar. 17, 2014
Business Combination, Consideration Transferred [Abstract]
Acquisition of business, payments	$ 1,375.8	$ 0							$ 1,172.1	$ 203.7
Asset Retirement Obligation [Abstract]
Discounted asset retirement obligation										101.7
Restricted Cash and Investments, Noncurrent [Abstract]
Funds for asset retirement obligation					189.2		14.5
Increase in funds for asset retirement obligation						$ 7		$ 4
Long-term Purchase Commitment [Line Items]
Purchase commitment, minimum quantity			545,000	270,000
Purchase commitment, maximum quantity			725,000