Business Segments (Details 2) (USD $) In Millions, unless otherwise specified	7 Months Ended		12 Months Ended
	Dec. 31, 2013		Dec. 31, 2014		May 31, 2013		May 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 4,765.9		$ 9,055.8		$ 9,974.1		$ 11,107.8
Long-lived assets	9,501.6		10,717.9
Goodwill	1,794.4		1,806.5		1,844.6
Deferred income taxes	152.2		394.4
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	1,249.8		1,921.4		2,069.3		2,161.6
Long-lived assets	122.2		257.6
Canpotex [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	439.7	[1]	923.6	[1]	1,239.8	[1]	1,298.9	[1]
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	259.7		663.1		686.3		786.3
Long-lived assets	5,372.3		4,993.0
India [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	315.8		331.9		475.2		1,579.7
Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	31.2		194.7		177.5		290.1
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	86.9		191.1		173.3		160.4
Argentina [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	163.1		167.3		258.3		266.7
Colombia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	55.2		145.0		143.5		155.9
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	75.9		131.5		188.2		177.5
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	22.4		131.3		128.9		90.5
Peru [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	35.6		101.8		56.9		95.1
Chile [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	76.9		44.6		116.5		121.1
Thailand [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	28.7		40.8		88.9		94.0
Other Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	72.4		223.7		271.7		209.3
Long-lived assets	51.0		22.5
Total Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	2,913.3		5,211.8		6,074.3		7,487.1
Long-lived assets	5,545.5		5,273.1
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	1,852.6		3,844.0		3,899.8		3,620.7
Long-lived assets	$ 3,956.1		$ 5,444.8

[1] The export association of the Saskatchewan potash producers.