ASSET RETIREMENT OBLIGATIONS (Reconciliations Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
ASSET RETIREMENT OBLIGATIONS [Abstract]
Balance at beginning of period	$ 220,581	$ 238,689	$ 226,594	$ 226,565
Liabilities incurred	505	4,339	505	6,159
Liabilities settled	(5,450)	(1,270)	(10,320)	(8,000)
Accretion expense	2,716	2,936	5,472	5,787
Revisions, net	(1,309)	(9,775)	(5,208)	4,408
Balance at end of period	$ 217,043	$ 234,919	$ 217,043	$ 234,919