Long-Term Debt (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended			1 Months Ended				12 Months Ended	1 Months Ended		3 Months Ended		12 Months Ended
	Sep. 24, 2013	Sep. 30, 2013	Dec. 31, 2013 item	Dec. 31, 2012	Nov. 30, 2012 Revolving Credit Facility [Member]	Sep. 24, 2013 Senior Secured Credit Facility [Member]	Dec. 31, 2013 Senior Secured Credit Facility [Member]	Sep. 24, 2013 Standby Letters Of Credit [Member]	Sep. 24, 2013 Swingline Loans [Member]	Dec. 31, 2013 Line Of Credit Facility [Member]	Jan. 24, 2012 ING Bank [Member]	Nov. 30, 2011 ING Bank [Member]	Sep. 30, 2013 ING Bank [Member]	Jun. 30, 2013 ING Bank [Member]	Dec. 31, 2013 ING Bank [Member]	Jun. 20, 2011 ING Bank [Member]
Line of Credit Facility [Line Items]
Deposit in association with covenant														$ 9,800,000	$ 2,500,000
Approximate amount of deposit that will be returned due to increased vessel valuations													7,300,000
Term of financing agreement in years					5 years											7 years
Line of Credit Facility, Current Borrowing Capacity	95,000,000
Maximum borrowing capacity	145,000,000
Repayments of long term lines of credit	46,600,000
Proceeds from borrowings of line of credit	21,000,000										12,700,000	6,100,000
Additional term loan amount	50,000,000					50,000,000
Lender commitments, minimum						15,000,000
Lender commitments, maximum						30,000,000
Long term debt carrying amount			198,229,000	237,630,000			21,000,000
Term loan facility principal amount						45,000,000
Line of credit						50,000,000		20,000,000	5,000,000
Line of Credit Facility, Amount Outstanding										3,700,000
Line of Credit Facility, Remaining Borrowing Capacity										25,300,000
Consolidated Leverage Ratio										4.50%
Future Consolidated Leverage Ratio										4.25%
Minimum Liquidity Amount										15,000,000
Minimum Future Liquidity Amount										20,000,000
Minimum Net Worth										228,000,000
Consolidated Net Income Earned										50.00%
Percent Of The Proceeds Of Issuances Of Equity Interests Received										100.00%
Line of Credit Facility, Bank Fees		800,000	1,400,000
Line of Credit Facility, Third Party Fees			148,000
Number Of Vessels Associated To Maintain Minimum Fair Value			5
Aggregate net book value of secured assets			422,300,000
2014			19,200,000
2015			20,300,000
2016			21,200,000
2017			44,900,000
2018			77,300,000
Thereafter			$ 15,300,000