Significant Operations (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended		12 Months Ended			12 Months Ended							12 Months Ended											12 Months Ended										3 Months Ended	12 Months Ended			1 Months Ended	60 Months Ended
	Jul. 31, 2013 item	Aug. 31, 2012 item	Dec. 31, 2013	Mar. 25, 2011 item	Dec. 31, 2006 item	Dec. 31, 2013 PCTC [Member] MSP [Member]	Dec. 31, 2012 PCTC [Member] MSP [Member]	Dec. 31, 2011 PCTC [Member] MSP [Member]	Dec. 31, 2013 Container Vessels [Member] MSP [Member]	Dec. 31, 2012 Container Vessels [Member] MSP [Member]	Dec. 31, 2011 Container Vessels [Member] MSP [Member]	Dec. 31, 2013 Special Purpose Vessels [Member] item	Dec. 31, 2013 Mini-Bulk Carrier [Member] T	Dec. 31, 2013 Capesize Bulk Carrier [Member] T	Dec. 31, 2013 Multi-Purpose Heavy Lift Vessel [Member] MSP [Member]	Dec. 31, 2013 Time Charter Contracts - U.S. Flag [Member]	Dec. 31, 2012 Time Charter Contracts - U.S. Flag [Member]	Dec. 31, 2011 Time Charter Contracts - U.S. Flag [Member]	Dec. 31, 2013 Time Charter Contracts - U.S. Flag [Member] PCTC [Member] item	Dec. 31, 2013 International Flag PCTC [Member] PCTC [Member]	Dec. 31, 2012 International Flag PCTC [Member] PCTC [Member]	Dec. 31, 2011 International Flag PCTC [Member] PCTC [Member]	Dec. 31, 2013 Rail-Ferry Service [Member] Terminales Transgolfo, S.A. de C.V. [Member]	Dec. 31, 2013 Rail-Ferry Service [Member] Special Purpose Vessels [Member]	Dec. 31, 2012 Rail-Ferry Service [Member] Special Purpose Vessels [Member]	Dec. 31, 2011 Rail-Ferry Service [Member] Special Purpose Vessels [Member]	Dec. 31, 2013 Jones Act [Member] TECO [Member]	Dec. 31, 2013 PCTC [Member] item	Dec. 31, 2013 PCTC [Member] United States [Member] item	Dec. 31, 2013 PCTC [Member] International [Member] item	Dec. 31, 2013 PCTC [Member] Supplemental Cargo [Member]	Dec. 31, 2012 PCTC [Member] Supplemental Cargo [Member]	Dec. 31, 2011 PCTC [Member] Supplemental Cargo [Member]	Mar. 31, 2012 PCTC [Member] Container Vessels [Member] item	Dec. 31, 2013 Bulk Carriers [Member]	Dec. 31, 2012 Bulk Carriers [Member]	Dec. 31, 2011 Bulk Carriers [Member]	Jul. 31, 2013 Bulk Carriers [Member] Mini-Bulk Carrier [Member] item	Dec. 31, 2013 Bulk Carriers [Member] Mini-Bulk Carrier [Member] item
Segment Reporting Information [Line Items]
Number of units						5			2										6								6								6
Revenue from major customer						$ 15,900	$ 17,900	$ 17,500	$ 5,600	$ 6,200	$ 5,900				$ 775	$ 36,500	$ 37,400	$ 32,800		$ 11,300	$ 13,500	$ 24,300		$ 37,200	$ 33,300	$ 36,300					$ 30,800	$ 44,700	$ 39,400		$ 21,100	$ 26,100	$ 19,700
Number of vessels owned or operated				2	2							2
Number of vessels sold																																		2
Concentration risk percentage																											33.50%
Percentage of total work force that is covered by collective bargaining agreements (in hundredths)			76.00%
Number of Pure Car Truck Carriers owned																			2
Number of Pure Car Truck Carriers with Buy Back Options																			3
Weight of diversified bulk carrier (in whole number)													8,028	170,578
Percentage of shareholders interest owned	23.70%																						49.00%															23.70%	25.00%
Number of vessels which deployed																												7	5	2
Number Of Mini Bulk Carriers Acquired																																							15
Number of vessels affected by stock issuance to unaffiliated co-investor	6																																					6
Number of Businesses Acquired		2