Quarterly Data-Unaudited (Details) $ / shares in Units, $ in Millions			3 Months Ended								12 Months Ended
	Jun. 17, 2015	Mar. 17, 2014 USD ($)	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares		Dec. 31, 2013 USD ($) $ / shares	Jul. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales			$ 1,115.8	$ 927.4	$ 1,311.5	$ 953.6	$ 1,216.5	$ 921.4	$ 1,472.7	$ 1,132.6	$ 4,308.3	$ 4,743.2		$ 5,474.7
Gross margin			280.4	165.0	685.9	415.8	444.3	301.1	590.3	442.8	1,547.1	1,778.5		2,520.2
Unrealized gains (losses) on derivatives			(97.5)	(125.9)	18.4	28.7	(40.4)	12.1	(28.6)	(22.6)	(176.3)	(79.5)
Net earnings attributable to common stockholders			$ 26.5	$ 90.9	$ 351.9	$ 230.6	$ 238.3	$ 130.9	$ 312.6	$ 708.5	$ 699.9	$ 1,390.3		$ 1,464.6
Net earnings per share attributable to common stockholders(1):
Basic (in dollars per share) | $ / shares			$ 0.11	$ 0.39	$ 1.50	$ 0.96	$ 0.97	$ 0.53	$ 1.22	$ 2.59	$ 2.97	$ 5.43	[1]	$ 4.97
Diluted (in dollars per share) | $ / shares			$ 0.11	$ 0.39	$ 1.49	$ 0.96	$ 0.96	$ 0.52	$ 1.22	$ 2.58	$ 2.96	$ 5.42	[1]	$ 4.95
Assets and Liabilities Held for Sale
Loss on sale of equity method investments											$ (42.8)	$ 0.0		$ 0.0
Gain on remeasurement of CF Fertilisers UK investment											94.4	0.0		0.0
Stock split, conversion ratio	5
Impairment of equity method investment in PLNL											61.9	$ 0.0		0.0
Phosphate mining and manufacturing business | Mosaic | Asset purchase agreement
Assets and Liabilities Held for Sale
After tax gain on sale of phosphate business										$ 461.0
Gain (loss) on disposal of discontinued operation, net of tax, per basic and diluted share (in dollars per share) | $ / shares										$ 1.68		$ 1.80
Gain on sale of phosphate business net of tax		$ 462.8
Keytrade AG | Non-operating equity method investments
Assets and Liabilities Held for Sale
After-tax loss on disposal					$ (29.2)
Loss on sale of equity method investments					$ (40.1)
Gain (loss) on disposal of discontinued operation, net of tax, per basic and diluted share (in dollars per share) | $ / shares					$ 0.12
PLNL | Operating equity method investments
Assets and Liabilities Held for Sale
After-tax loss on disposal			$ 61.9
Gain (loss) on disposal of discontinued operation, net of tax, per basic and diluted share (in dollars per share) | $ / shares			$ 0.26
Impairment of equity method investment in PLNL			$ 61.9									$ 0.0		$ 0.0
CF Fertilisers UK
Assets and Liabilities Held for Sale
Gain on remeasurement of CF Fertilisers UK investment				$ 94.4							$ 94.4
Business acquisition, initial percentage of ownership															50.00%
Gain (loss) on disposal of discontinued operation, net of tax, per basic and diluted share (in dollars per share) | $ / shares				$ 0.40

[1] Share and per share amounts have been retroactively restated for all prior periods presented to reflect the five-for-one split of the Company’s common stock effected in the form of a stock dividend that was distributed on June 17, 2015.