LEASES (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Line Items]
Operating leases, rent expense	$ 91,587	$ 91,947	$ 91,875
Office Space [Member]
Leases [Line Items]
Operating leases, rent expense	647	$ 1,324	$ 1,808
Charters-Out [Member]
Leases [Line Items]
Operating leases, future minimum payments receivable, current	177,283
Operating leases, future minimum payments receivable, in two years	94,961
Operating leases, future minimum payments receivable, in three years	43,570
Charters-Out [Member] | Contract of Affreightmen [Member]
Leases [Line Items]
Operating leases, future minimum payments receivable, current	22,698
Operating leases, future minimum payments receivable, in two years	23,031
Operating leases, future minimum payments receivable, in three years	$ 6,356