Segment Disclosures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 item	Jun. 30, 2013	Dec. 31, 2013
Segment Disclosures
Number of business segments			2
Segment data
Net sales	$ 1,472.7	$ 1,714.9	$ 2,605.3	$ 3,051.4
Cost of sales	882.4	849.7	1,572.2	1,511.1
Gross margin	590.3	865.2	1,033.1	1,540.3
Total other operating costs and expenses	61.1	41.0	97.0	99.9
Gain on sale of phosphate business			747.1
Equity in earnings of operating affiliates	2.1	9.5	17.9	21.1
Operating earnings (Loss)	531.3	833.7	1,701.1	1,461.5
Assets	11,304.9		11,304.9		10,678.1
Ammonia
Segment data
Net sales	604.8	586.8	877.2	787.2
Granular urea
Segment data
Net sales	267.6	271.1	483.8	534.7
UAN
Segment data
Net sales	456.5	556.1	856.4	1,094.0
AN
Segment data
Net sales	73.9	65.2	132.1	120.1
DAP
Segment data
Net sales	21.0	137.4	127.5	334.0
MAP
Segment data
Net sales	2.3	52.3	40.9	94.6
Other
Segment data
Net sales	46.6	46.0	87.4	86.8
Operating segments | Nitrogen
Segment data
Net sales	1,449.4	1,525.2	2,436.9	2,622.8
Cost of sales	860.7	678.0	1,413.9	1,128.0
Gross margin	588.7	847.2	1,023.0	1,494.8
Assets	7,446.7		7,446.7		6,913.8
Operating segments | Nitrogen | Ammonia
Segment data
Net sales	604.8	586.8	877.2	787.2
Operating segments | Nitrogen | Granular urea
Segment data
Net sales	267.6	271.1	483.8	534.7
Operating segments | Nitrogen | UAN
Segment data
Net sales	456.5	556.1	856.4	1,094.0
Operating segments | Nitrogen | AN
Segment data
Net sales	73.9	65.2	132.1	120.1
Operating segments | Nitrogen | Other
Segment data
Net sales	46.6	46.0	87.4	86.8
Operating segments | Phosphate
Segment data
Net sales	23.3	189.7	168.4	428.6
Cost of sales	21.7	171.7	158.3	383.1
Gross margin	1.6	18.0	10.1	45.5
Assets	36.0		36.0		817.6
Operating segments | Phosphate | DAP
Segment data
Net sales	21.0	137.4	127.5	334.0
Operating segments | Phosphate | MAP
Segment data
Net sales	2.3	52.3	40.9	94.6
Other
Segment data
Assets	$ 3,822.2		$ 3,822.2		$ 2,946.7