Revenue - Revenue Disaggregated by Product (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Net sales	$ 86,062	$ 88,582	$ 137,660	$ 91,873	$ 98,117	$ 79,909	$ 93,197	$ 79,859	$ 404,177	$ 351,082	$ 330,802
Net sales, exclusive of freight and other
Disaggregation of Revenue [Line Items]
Net sales									363,096	309,216
Ammonia
Disaggregation of Revenue [Line Items]
Net sales									94,467	66,254
UAN
Disaggregation of Revenue [Line Items]
Net sales									251,199	222,329
Urea products
Disaggregation of Revenue [Line Items]
Net sales									17,430	20,633
Freight revenue
Disaggregation of Revenue [Line Items]
Net sales									33,436	33,567
Other revenue
Disaggregation of Revenue [Line Items]
Net sales									$ 7,645	$ 8,299