LEASES (Bareboat Charters-In) (Details) - Bareboat Charters-In [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Leases [Line Items]
2018	$ 91,457
2019	111,819
2020	9,168
2021	9,143
2022	9,143
Thereafter	22,846
Net minimum lease payments	$ 253,576
2018, operating days	3650 days
2019, operating days	3470 days
2020, operating days	366 days
2021, operating days	365 days
2022, operating days	365 days
Thereafter, operating days	912 days
Operating days, total	9128 days