SEGMENT DATA (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
SEGMENT DATA [Abstract]
Number of reportable segments | Segment			2
Revenues [Abstract]
Marine transportation	$ 359,031,000	$ 418,343,000	$ 1,115,677,000	$ 1,263,301,000
Diesel engine services	75,677,000	114,222,000	219,346,000	400,093,000
Total revenues	434,708,000	532,565,000	1,335,023,000	1,663,394,000
Segment profit (loss)	51,559,000	90,623,000	175,376,000	281,597,000
Total assets	4,223,827,000		4,223,827,000		$ 4,152,281,000
Other segment disclosures [Abstract]
Gain (loss) on disposition of assets	(122,000)	(400,000)	39,000	1,246,000
Interest expense	(4,507,000)	(4,449,000)	(13,213,000)	(14,458,000)
Other income (expense)	(120,000)	22,000	194,000	(221,000)
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(8,535,000)	(8,638,000)	(24,465,000)	(24,718,000)
Total assets	59,963,000		59,963,000		63,179,000
Other segment disclosures [Abstract]
General corporate expenses	(3,786,000)	(3,811,000)	(11,485,000)	(11,285,000)
Gain (loss) on disposition of assets	(122,000)	(400,000)	39,000	1,246,000
Interest expense	(4,507,000)	(4,449,000)	(13,213,000)	(14,458,000)
Other income (expense)	(120,000)	22,000	194,000	(221,000)
Loss from other segment	(8,535,000)	(8,638,000)	(24,465,000)	(24,718,000)
Details of "Other" total assets [Abstract]
General corporate assets	57,453,000		57,453,000		61,089,000
Investment in affiliates	2,510,000		2,510,000		2,090,000
Total other assets	59,963,000		59,963,000		63,179,000
Reporting Segments [Member] | Marine Transportation [Member]
Revenues [Abstract]
Marine transportation	359,031,000	418,343,000	1,115,677,000	1,263,301,000
Segment profit (loss)	55,460,000	93,650,000	197,981,000	286,930,000
Total assets	3,571,510,000		3,571,510,000		3,451,553,000
Reporting Segments [Member] | Diesel Engine Services [Member]
Revenues [Abstract]
Diesel engine services	75,677,000	114,222,000	219,346,000	400,093,000
Segment profit (loss)	4,634,000	5,611,000	1,860,000	19,385,000
Total assets	592,354,000		592,354,000		$ 637,549,000
Intersegment Eliminations [Member] | Marine Transportation [Member]
Revenues [Abstract]
Total revenues	7,171,000	7,032,000	17,722,000	20,322,000
Segment profit (loss)	$ 717,000	$ 703,000	$ 1,772,000	$ 2,032,000