SUPPLEMENTAL CASH FLOW INFORMATION - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of amount capitalized	$ 34,970	$ 35,919	$ 40,747
Income taxes paid	2,193	562	8,114
Noncash investing activities:
Accrued development, exploration costs and other capital	74,909	79,988	79,206
Capitalized asset retirement obligations costs	1,354	230	981
Noncash financing activities:
Issuance of common stock for employee benefit plans	9,536	6,675	5,758
Treasury stock acquired in connection with tax withholdings	$ 3,293	$ 2,610	$ 4,722