REVENUE (Disaggregation of Revenue) (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
Potash [Member]
Disaggregation of Revenue [Line Items]
Revenue									$ 104,467		$ 107,471		$ 95,540
Trio [Member]
Disaggregation of Revenue [Line Items]
Revenue									64,299		64,139		63,338
Water Product [Member]
Disaggregation of Revenue [Line Items]
Revenue									25,657		19,797		7,042
Salt [Member]
Disaggregation of Revenue [Line Items]
Revenue									4,907		6,804		6,334
Magnesium Chloride [Member]
Disaggregation of Revenue [Line Items]
Revenue									12,779		6,877		5,432
Brines [Member]
Disaggregation of Revenue [Line Items]
Revenue									2,493		1,777		229
Product and Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									5,473		1,405
Mineral [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 48,849	$ 51,160	$ 62,512	$ 57,554	$ 54,364	$ 41,410	$ 55,176	$ 57,320	220,075	[1]	208,270	[1]	177,915	[1]
Potash [Member] | Potash [Member]
Disaggregation of Revenue [Line Items]
Revenue									103,403		107,471		95,540
Potash [Member] | Trio [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Potash [Member] | Water Product [Member]
Disaggregation of Revenue [Line Items]
Revenue									1,823		1,368		441
Potash [Member] | Salt [Member]
Disaggregation of Revenue [Line Items]
Revenue									4,907		6,804		6,275
Potash [Member] | Magnesium Chloride [Member]
Disaggregation of Revenue [Line Items]
Revenue									12,022		6,638		5,432
Potash [Member] | Brines [Member]
Disaggregation of Revenue [Line Items]
Revenue									2,493		1,777		229
Potash [Member] | Product and Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0
Potash [Member] | Mineral [Member]
Disaggregation of Revenue [Line Items]
Revenue									124,648		124,058		107,917
Trio [Member] | Potash [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Trio [Member] | Trio [Member]
Disaggregation of Revenue [Line Items]
Revenue									64,299		64,139		63,338
Trio [Member] | Water Product [Member]
Disaggregation of Revenue [Line Items]
Revenue									4,495		2,430		289
Trio [Member] | Salt [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		59
Trio [Member] | Magnesium Chloride [Member]
Disaggregation of Revenue [Line Items]
Revenue									757		239		0
Trio [Member] | Brines [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Trio [Member] | Product and Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0
Trio [Member] | Mineral [Member]
Disaggregation of Revenue [Line Items]
Revenue									69,551		66,808		63,686
Oil Field Solutions [Member] | Potash [Member]
Disaggregation of Revenue [Line Items]
Revenue									2,973		0		0
Oil Field Solutions [Member] | Trio [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Oil Field Solutions [Member] | Water Product [Member]
Disaggregation of Revenue [Line Items]
Revenue									19,339		15,999		6,312
Oil Field Solutions [Member] | Salt [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Oil Field Solutions [Member] | Magnesium Chloride [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Oil Field Solutions [Member] | Brines [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Oil Field Solutions [Member] | Product and Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									5,582		1,405
Oil Field Solutions [Member] | Mineral [Member]
Disaggregation of Revenue [Line Items]
Revenue									27,894		17,404		6,312
Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue									(2,018)		0		0
Intersegment Eliminations [Member] | Potash [Member]
Disaggregation of Revenue [Line Items]
Revenue									(1,909)		0		0
Intersegment Eliminations [Member] | Trio [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Intersegment Eliminations [Member] | Water Product [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Intersegment Eliminations [Member] | Salt [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0
Intersegment Eliminations [Member] | Magnesium Chloride [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		0
Intersegment Eliminations [Member] | Brines [Member]
Disaggregation of Revenue [Line Items]
Revenue									0		0		$ 0
Intersegment Eliminations [Member] | Product and Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									$ (109)		$ 0

[1] Segment sales include the sales of byproducts generated during the production of potash and Trio®.