LEASES (Components of Nonmineral Lease Expense) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
LEASES [Abstract]
Operating lease cost		$ 14,057		$ 42,352
Short-term lease cost	[1]	8,756		25,378
Variable lease cost		3,637		10,194
Sublease income		(774)		(2,192)
Total lease cost		$ 25,676	$ 22,539	$ 75,732	$ 68,859

[1] We have elected to recognize the cost of leases with an initial term of one month or less within our short-term lease cost.