SEGMENT DATA (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Segment	Jun. 30, 2012	Dec. 31, 2012
SEGMENT DATA [Abstract]
Number of Reportable Segments			2
Revenues [Abstract]
Marine transportation	$ 423,868	$ 342,195	$ 842,386	$ 678,152
Diesel engine services	140,040	169,653	280,307	400,631
Total revenues	563,908	511,848	1,122,693	1,078,783
Segment profit (loss)	102,134	77,827	194,070	161,196
Total assets	3,724,309		3,724,309		3,653,128
Other segment disclosures [Abstract]
Loss on disposition of assets	537	69	505	41
Interest expense	(7,219)	(5,901)	(15,207)	(11,741)
Other income	101	30	176	179
Details of "Other" total assets [Abstract]
Total assets	3,724,309		3,724,309		3,653,128
Marine transportation [Member]
Revenues [Abstract]
Marine transportation	97,563	71,730	186,816	140,220
Total assets	3,054,231		3,054,231		2,951,723
Details of "Other" total assets [Abstract]
Total assets	3,054,231		3,054,231		2,951,723
Diesel engine services [Member]
Revenues [Abstract]
Diesel engine services	14,932	15,118	28,954	38,672
Total assets	616,496		616,496		647,986
Details of "Other" total assets [Abstract]
Total assets	616,496		616,496		647,986
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(10,361)	(9,021)	(21,700)	(17,696)
Total assets	53,582		53,582		53,419
Other segment disclosures [Abstract]
General corporate expenses	(3,780)	(3,219)	(7,174)	(6,175)
Loss on disposition of assets	537	69	505	41
Interest expense	(7,219)	(5,901)	(15,207)	(11,741)
Other income	101	30	176	179
Profit (loss) from other segment	(10,361)	(9,021)	(21,700)	(17,696)
Details of "Other" total assets [Abstract]
General corporate assets	51,574		51,574		51,611
Investment in affiliates	2,008		2,008		1,808
Total assets	$ 53,582		$ 53,582		$ 53,419