CAPITAL STOCK - Activity of Common Stock Outstanding (Details) - Common Stock - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Roll Forward]
Balance, beginning of period (in shares)	17,316	17,197	14,390
Issuance of shares for compensation net of withholding (in shares)	85	119	84
Issuance of common stock related to equity distribution agreements (in shares)	0	0	2,723
Balance, end of period (in shares)	17,401	17,316	17,197