REVENUE RECOGNITION - Revenue Disaggregated by Product or Service (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	$ 290,989	$ 276,993
North America
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	50,052	65,287
Other Regions
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	240,937	$ 211,706
Product revenue | North America
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	46,457
Product revenue | Other Regions
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	226,907
Processing and other revenues | North America
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	3,595
Processing and other revenues | Other Regions
Disaggregation of Revenue [Line Items]
Total sales and other operating revenues	$ 14,030