Major Customers and Suppliers (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Sales | Customer concentration | Nitrogen Fertilizer
Major Customers and Suppliers
Concentration risk (as a percent)	28.00%	20.00%	29.00%
Sales | Customer concentration | Nitrogen Fertilizer | Customer A
Major Customers and Suppliers
Concentration risk (as a percent)	15.00%	10.00%	17.00%
Sales | Customer concentration | Nitrogen Fertilizer | Customer B
Major Customers and Suppliers
Concentration risk (as a percent)	13.00%	10.00%	12.00%
Direct operating expenses (exclusive of depreciation and amortization) | Supplier concentration
Major Customers and Suppliers
Number of major suppliers	1
Direct operating expenses (exclusive of depreciation and amortization) | Supplier concentration | Supplier A
Major Customers and Suppliers
Concentration risk (as a percent)	4.00%	5.00%	5.00%