Stockholders' Equity (Details 5) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 31, 2015
Reclassification out of AOCI
Equity in earnings of non-operating affiliates—net of taxes	$ 72.3	$ 22.5	$ 9.6
Available-for-sale securities	1.6	0.9	4.7
Reclassification to earnings	6.8	29.9	11.6
Tax effect	(395.8)	(773.0)	(686.5)
Net earnings	734.1	1,436.8	1,532.8
CF Fertilisers UK
Reclassification out of AOCI
Reclassification to earnings	47.2
Defined Benefit Plans
Business acquisition, initial percentage of ownership				50.00%
Unrealized Gain (Loss) on Securities
Reclassification out of AOCI
Reclassification to earnings	0.9	(0.4)	(0.6)
Unrealized Gain (Loss) on Derivatives
Reclassification out of AOCI
Reclassification to earnings	0.0	(2.8)
Defined Benefit Plans
Reclassification out of AOCI
Reclassification to earnings	5.9	33.1	12.2
Defined Benefit Plans | CF Fertilisers UK
Reclassification out of AOCI
Reclassification to earnings	38.2
Foreign Currency Translation Adjustment | CF Fertilisers UK
Reclassification out of AOCI
Reclassification to earnings	9.0
Amount reclassified from AOCI
Reclassification out of AOCI
Net earnings	51.4	18.9	7.5
Amount reclassified from AOCI | Unrealized Gain (Loss) on Securities
Reclassification out of AOCI
Available-for-sale securities	0.9	(0.4)	(0.6)
Total before tax	0.9	(0.4)	(0.6)
Tax effect	(0.5)	0.1	0.2
Net earnings	0.4	(0.3)	(0.4)
Amount reclassified from AOCI | Unrealized Gain (Loss) on Derivatives
Reclassification out of AOCI
Reclassification of de-designated hedges	0.0	(2.8)	0.0
Total before tax	0.0	(2.8)	0.0
Tax effect	0.0	1.0	0.0
Net earnings	0.0	(1.8)	0.0
Amount reclassified from AOCI | Defined Benefit Plans
Reclassification out of AOCI
Amortization of prior service cost	(1.0)	(0.4)	0.3
Reclassification to earnings	38.2	0.0	0.0
Amortization of net loss	6.9	33.5	11.9
Total before tax	44.1	33.1	12.2
Tax effect	(2.1)	(12.1)	(4.3)
Net earnings	42.0	21.0	7.9
Amount reclassified from AOCI | Foreign Currency Translation Adjustment
Reclassification out of AOCI
Equity in earnings of non-operating affiliates—net of taxes	9.0	0.0	0.0
Total before tax	9.0	0.0	0.0
Tax effect	0.0	0.0	0.0
Net earnings	$ 9.0	$ 0.0	$ 0.0