FAIR VALUE - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset retirement obligations	$ 259	$ 226
Second Lien Notes due 2023 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of senior unsecured notes	$ 194,900		$ 434,400