SEGMENT DATA (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Segment	Sep. 30, 2013	Dec. 31, 2013
SEGMENT DATA [Abstract]
Number of Reportable Segments			2
Revenues [Abstract]
Marine transportation	$ 448,744	$ 436,181	$ 1,341,260	$ 1,278,567
Diesel engine services	231,977	114,924	556,761	395,231
Total revenues	680,721	551,105	1,898,021	1,673,798
Segment profit (loss)	122,928	111,703	345,607	305,773
Total assets	3,952,134		3,952,134		3,682,517
Other segment disclosures [Abstract]
Gain (loss) on disposition of assets	47	223	625	728
Interest expense	(5,225)	(6,694)	(16,312)	(21,901)
Other income (expense)	27	60	(86)	236
Details of "Other" total assets [Abstract]
Total assets	3,952,134		3,952,134		3,682,517
Marine transportation [Member]
Revenues [Abstract]
Segment profit (loss)	112,141	113,647	325,660	300,463
Total assets	3,220,965		3,220,965		3,046,692
Details of "Other" total assets [Abstract]
Total assets	3,220,965		3,220,965		3,046,692
Diesel engine services [Member]
Revenues [Abstract]
Segment profit (loss)	20,027	9,077	47,136	38,031
Total assets	676,862		676,862		576,472
Details of "Other" total assets [Abstract]
Total assets	676,862		676,862		576,472
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(9,240)	(11,021)	(27,189)	(32,721)
Total assets	54,307		54,307		59,353
Other segment disclosures [Abstract]
General corporate expenses	(4,089)	(4,610)	(11,416)	(11,784)
Gain (loss) on disposition of assets	47	223	625	728
Interest expense	(5,225)	(6,694)	(16,312)	(21,901)
Other income (expense)	27	60	(86)	236
Profit (loss) from other segment	(9,240)	(11,021)	(27,189)	(32,721)
Details of "Other" total assets [Abstract]
General corporate assets	51,885		51,885		57,197
Investment in affiliates	2,422		2,422		2,156
Total assets	$ 54,307		$ 54,307		$ 59,353