Gain on Sale/Purchase of Other Assets (Details) (USD $)	1 Months Ended	3 Months Ended			9 Months Ended
	Mar. 31, 2012	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Gain on Sale/Purchase 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	(3,000)		0	4,463,000	0
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