Goodwill and Intangible Assets, Net (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset $ 82.7   $ 88.1
Accumulated amortization (17.8)   (17.3)
Net finite-lived intangible assets 64.9   70.8
Amortization expense 1.1 0.5  
Acquired Indefinite-lived Intangible Assets [Line Items]      
Goodwill 63.1   68.5
Water Rights [Member]      
Acquired Indefinite-lived Intangible Assets [Line Items]      
Indefinite-lived intangible assets 22.9   22.9
Trade Names [Member]      
Acquired Indefinite-lived Intangible Assets [Line Items]      
Indefinite-lived intangible assets 11.3   12.4
Plant Nutrition [Member]      
Acquired Indefinite-lived Intangible Assets [Line Items]      
Goodwill 56.7   62.0
Supply Agreement      
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset 28.6   31.3
Accumulated amortization (2.4)   (2.5)
Net finite-lived intangible assets 26.2   28.8
Average useful life 50 years    
SOP Production Rights [Member]      
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset 24.3   24.3
Accumulated amortization (11.0)   (10.8)
Net finite-lived intangible assets 13.3   13.5
Average useful life 25 years    
Patents [Member]      
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset 16.3   17.9
Accumulated amortization (1.4)   (1.2)
Net finite-lived intangible assets 14.9   16.7
Patents [Member] | Minimum [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 10 years    
Patents [Member] | Maximum [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 20 years    
Developed Technology [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 5 years    
Lease Rights [Member]      
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset 1.8   1.9
Accumulated amortization (0.2)   (0.2)
Net finite-lived intangible assets 1.6   1.7
Average useful life 25 years    
Customer and Distributor Relationships [Member]      
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset 7.4   8.1
Accumulated amortization (2.0)   (2.0)
Net finite-lived intangible assets 5.4   6.1
Customer and Distributor Relationships [Member] | Minimum [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 5 years    
Customer and Distributor Relationships [Member] | Maximum [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 10 years    
Trademarks [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 10 years    
Noncompete Agreements [Member]      
Finite-Lived Intangible Assets [Line Items]      
Average useful life 5 years    
Other [Member]      
Finite-Lived Intangible Assets [Line Items]      
Gross intangible asset 4.3   4.6
Accumulated amortization (0.8)   (0.6)
Net finite-lived intangible assets $ 3.5   $ 4.0