v3.3.1.900
Major Customers and Suppliers (Details) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Major Customers and Suppliers      
Insurance coverage limit $ 200,000,000    
Sales | Customer concentration | Nitrogen Fertilizer      
Major Customers and Suppliers      
Concentration risk (as a percent) 24.00% 27.00% 28.00%
Sales | Customer concentration | Nitrogen Fertilizer | Customer A      
Major Customers and Suppliers      
Concentration risk (as a percent) 10.00% 17.00% 15.00%
Sales | Customer concentration | Nitrogen Fertilizer | Customer B      
Major Customers and Suppliers      
Concentration risk (as a percent) 14.00% 10.00% 13.00%