Gain on Sale of Other Assets (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended
	Mar. 31, 2012 item	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2012 US Flag PCTC Vessel [Member] item	Jun. 30, 2012 Molten Sulphur Carrier [Member] item
Property, Plant and Equipment [Line Items]
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	(6,000)	(3,000)	(6,000)	4,463,000
Repayments of debt from sale proceeds	36,100,000
Deferred gain on purchase of property						$ 239,000	$ 430,000
Number of vessel sold						1	1