Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total	$ 295,850	$ 273,945	$ 1,102,457	$ 1,083,383
Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	31,835	45,022	187,700	236,895
Primary nutrients
Disaggregation of Revenue [Line Items]
Total	62,094	71,343	296,247	322,130
Service
Disaggregation of Revenue [Line Items]
Total	13,119	16,688	37,334	53,324
Products and co-products
Disaggregation of Revenue [Line Items]
Total	152,938	82,813	446,919	255,029
Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	21,676	47,188	92,990	184,418
Other
Disaggregation of Revenue [Line Items]
Total	14,188	10,891	41,267	31,587
Trade
Disaggregation of Revenue [Line Items]
Total	81,335	114,462	282,519	441,263
Trade | Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	0	9,840	0	45,648
Trade | Primary nutrients
Disaggregation of Revenue [Line Items]
Total	0	4,610	0	27,401
Trade | Service
Disaggregation of Revenue [Line Items]
Total	2,010	2,507	6,053	11,077
Trade | Products and co-products
Disaggregation of Revenue [Line Items]
Total	55,235	48,158	171,744	166,859
Trade | Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	21,676	47,188	92,990	184,418
Trade | Other
Disaggregation of Revenue [Line Items]
Total	2,414	2,159	11,732	5,860
Ethanol
Disaggregation of Revenue [Line Items]
Total	98,216	38,005	276,656	98,538
Ethanol | Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Ethanol | Primary nutrients
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Ethanol | Service
Disaggregation of Revenue [Line Items]
Total	0	3,187	0	10,170
Ethanol | Products and co-products
Disaggregation of Revenue [Line Items]
Total	97,703	34,655	275,175	88,170
Ethanol | Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Ethanol | Other
Disaggregation of Revenue [Line Items]
Total	513	163	1,481	198
Plant Nutrient
Disaggregation of Revenue [Line Items]
Total	102,707	109,446	507,445	508,548
Plant Nutrient | Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	31,835	35,182	187,700	191,247
Plant Nutrient | Primary nutrients
Disaggregation of Revenue [Line Items]
Total	62,094	66,733	296,247	294,729
Plant Nutrient | Service
Disaggregation of Revenue [Line Items]
Total	975	1,275	3,753	3,133
Plant Nutrient | Products and co-products
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Plant Nutrient | Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Plant Nutrient | Other
Disaggregation of Revenue [Line Items]
Total	7,803	6,256	19,745	19,439
Rail
Disaggregation of Revenue [Line Items]
Total	13,592	12,032	35,837	35,034
Rail | Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Rail | Primary nutrients
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Rail | Service
Disaggregation of Revenue [Line Items]
Total	10,134	9,719	27,528	28,944
Rail | Products and co-products
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Rail | Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Rail | Other
Disaggregation of Revenue [Line Items]
Total	$ 3,458	$ 2,313	$ 8,309	$ 6,090