COMMITMENTS AND CONTINGENCIES - Commercial Commitments Outstanding (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Other Commitments
Less Than 1 Year	$ 40,877
1-3 Years	23,897
3-5 Years	0
More Than 5 Years	2,272
Total Amounts Committed	67,046
Purchase obligations
Other Commitments
Less Than 1 Year	40,428
1-3 Years	23,897
3-5 Years	0
More Than 5 Years	0
Total Amounts Committed	64,325
Letters of credit and surety bonds
Other Commitments
Less Than 1 Year	449
1-3 Years	0
3-5 Years	0
More Than 5 Years	2,272
Total Amounts Committed	$ 2,721