REVENUE (Schedule of Contract with Customer, Asset and Liability) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Change In Contract With Customer, Asset [Roll Forward]
Beginning balance	$ 0	$ 0
Consideration earned during the period	0	(35,834)
Consideration received during the period	0	35,834
Ending balance	0	0
Change In Contract With Customer, Liability [Roll Forward]
Beginning balance	296,496	179,179
Consideration earned during the period	(166,485)	(308,898)
Consideration received during the period	57,925	426,215
Ending balance	$ 187,936	$ 296,496