Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total	$ 459,105	$ 494,266	$ 806,607	$ 809,438
Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	82,634	119,535	155,865	191,873
Primary nutrients
Disaggregation of Revenue [Line Items]
Total	188,463	197,271	234,153	250,787
Service
Disaggregation of Revenue [Line Items]
Total	13,611	22,266	24,215	36,636
Products and co-products
Disaggregation of Revenue [Line Items]
Total	139,117	87,990	293,981	172,218
Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	21,439	56,767	71,314	137,230
Other
Disaggregation of Revenue [Line Items]
Total	13,841	10,437	27,079	20,694
Trade
Disaggregation of Revenue [Line Items]
Total	92,470	177,226	201,184	326,797
Trade | Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	0	31,870	0	35,808
Trade | Primary nutrients
Disaggregation of Revenue [Line Items]
Total	0	22,364	0	22,791
Trade | Service
Disaggregation of Revenue [Line Items]
Total	2,357	7,745	4,043	8,570
Trade | Products and co-products
Disaggregation of Revenue [Line Items]
Total	63,344	55,943	116,509	118,701
Trade | Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	21,439	56,767	71,314	137,230
Trade | Other
Disaggregation of Revenue [Line Items]
Total	5,330	2,537	9,318	3,697
Ethanol
Disaggregation of Revenue [Line Items]
Total	76,125	35,629	178,440	60,535
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	3,547	0	6,983
Ethanol | Products and co-products
Disaggregation of Revenue [Line Items]
Total	75,773	32,047	177,472	53,517
Ethanol | Frac sand and propane
Disaggregation of Revenue [Line Items]
Total	0	0	0	0
Ethanol | Other
Disaggregation of Revenue [Line Items]
Total	352	35	968	35
Plant Nutrient
Disaggregation of Revenue [Line Items]
Total	279,825	270,577	404,738	399,102
Plant Nutrient | Specialty nutrients
Disaggregation of Revenue [Line Items]
Total	82,634	87,665	155,865	156,065
Plant Nutrient | Primary nutrients
Disaggregation of Revenue [Line Items]
Total	188,463	174,907	234,153	227,996
Plant Nutrient | Service
Disaggregation of Revenue [Line Items]
Total	2,596	1,696	2,778	1,858
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	6,132	6,309	11,942	13,183
Rail
Disaggregation of Revenue [Line Items]
Total	10,685	10,834	22,245	23,004
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	8,658	9,278	17,394	19,225
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	$ 2,027	$ 1,556	$ 4,851	$ 3,779