Subsequent Events (Details) (USD $)	6 Months Ended		12 Months Ended		0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Subsequent Event [Member] Vessel Investment [Member] Tanker	Aug. 01, 2013 Subsequent Event [Member] Series B Cumulative Redeemable Perpetual Preferred Stock Issuance [Member] Payment	Aug. 02, 2013 Subsequent Event [Member] Repayment of Debt [Member] InterestRateSwap Vessel
Subsequent Event [Line Items]
Net proceeds from the issuance of preferred stock	$ 23,480,000	$ 0			$ 30,200,000
Number of share issued to public (in shares)					275,000
Liquidation preference price (in dollars per share)					$ 100.00
Underwriter overallotmment					4,100,000
Number of days to exercise underwriter overallotment					30 days
Initial dividend rate (in hundredths)	9.50%		9.50%		9.00%
Number of days to redeem shares after a change of control					120 days
Number of payments in arrears for certain voting rights to be effective					6
Deposit paid on handysize bulk carrier newbuilding				1,900,000
Number of newly-built chemical tankers committed to purchase a minority interest in				2
Total value of investment				8,500,000
Amount of investment due in third quarter of 2013				3,000,000
Amount of investment due upon delivery of vessel				5,500,000
Early Debt Pay Off [Abstract]
Number of vessels on which principal and interest was repaid						1
Early settlement of debt						11,361,696.27
Number of effective interest rate swap included						2
Percentage of outstanding principal covered by each swap						50.00%
Settlement due for unwinding of instruments						$ 800,000