Gain on Sale of Other Assets (Details) (USD $)	1 Months Ended	3 Months Ended			6 Months Ended
	Mar. 31, 2012 InterestRateSwap	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2013	Jun. 30, 2012
Gain on Sale of Other Assets [Abstract]
Number of International Flag Pure Car Truck Carriers sold	2
Proceeds from sale of other assets	$ 73,900,000
Gain on sale of other assets	3,800,000	0	667,000		0	4,466,000
Repayments of debt from sale proceeds				36,100,000
US Flag PCTC Vessel [Member]
Property, Plant and Equipment [Line Items]
Deferred gain on purchase of property						239,000
Number of vessel sold						1
Molten Sulphur Carrier [Member]
Property, Plant and Equipment [Line Items]
Deferred gain on purchase of property						$ 430,000
Number of vessel sold						1