LONG-TERM DEBT (Details) (USD $)			12 Months Ended			1 Months Ended	12 Months Ended		1 Months Ended						1 Months Ended				12 Months Ended		12 Months Ended				12 Months Ended							12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended						12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Revolving Credit Facility [Member]	Nov. 28, 2012 Revolving Credit Facility [Member]	Jul. 15, 2011 Revolving Credit Facility [Member]	Jan. 31, 2013 Revolving Credit Facility One [Member]	Dec. 31, 2012 Revolving Credit Facility One [Member]	Jun. 20, 2011 ING Bank [Member]	Jul. 31, 2011 DNB Nor Bank ASA [Member]	Jun. 30, 2011 DNB Nor Bank ASA [Member]	Jun. 29, 2011 DNB Nor Bank ASA [Member]	Nov. 30, 2012 Capital One N.A [Member]	Dec. 31, 2012 Notes Payable - Variable Rate 2015 [Member]	Dec. 31, 2012 Notes Payable - Variable Rate 2012 [Member]	Jun. 30, 2011 Notes Payable - Variable Rate 2018, Tranche A [Member]	Jan. 31, 2012 Notes Payable - Variable Rate 2018, Tranche B [Member]	Nov. 30, 2011 Notes Payable - Variable Rate 2018, Tranche B [Member]	Jun. 20, 2011 Notes Payable - Variable Rate 2018, Tranche B [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2015 [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2015 [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2012 [Member]		Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2012 [Member]		Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2013 [Member]		Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2013 [Member]		Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2013 [Member] Interest Rate Swap One [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2013 [Member] Interest Rate Swap Two [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2013 [Member] Interest Rate Swap Three [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche A [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche A [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche B [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche B [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018b [Member]		Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018b [Member]		Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018c [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018c [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member] Maximum [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member] Maximum [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member] Minimum [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member] Minimum [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2014 [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2014 [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2020 [Member]		Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2020 [Member]		Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2017 [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2017 [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable - Variable Rate 2017b [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable - Variable Rate 2017b [Member]	Dec. 31, 2012 Secured Debt [Member] Notes Payable Variable Rate 2017c [Member]	Dec. 31, 2011 Secured Debt [Member] Notes Payable Variable Rate 2017c [Member]	Dec. 31, 2012 Unsecured Line of Credit [Member]	Dec. 31, 2011 Unsecured Line of Credit [Member]
Long-term Debt [Abstract]
Interest rate (in hundredths)																			2.06%	1.5738%			0.00%	[1]			1.8293%	[2]				2.809%	3.0632%	2.8158%	3.00%			3.2458%	[3]	2.981%	3.2458%								3.2702%	1.8314%	[4]	1.0957%	[4]		3.06%	2.559%	2.644%	2.709%		3.9597%	4.0349%
Interest rate, minimum (in hundredths)																																														2.81%	2.88%
Interest rate, maximum (in hundredths)																																												2.85%	2.92%
Maturity date																			2015		2012	[1]			2013	[2]						2018		2018		2018	[3]			2018		2018						2014		2020	[4]			2017		2017		2017		2014
Total principal due	$ 237,630,000	$ 322,093,000																	$ 12,666,000	$ 15,333,000	$ 0	[1]	$ 12,845,000	[1]	$ 0	[2]	$ 29,389,000	[2]				$ 18,896,000	$ 22,332,000	$ 17,908,000	$ 6,175,000	$ 0	[3]	$ 24,162,000	[3]	$ 15,620,000	$ 18,460,000	$ 48,760,000	$ 52,440,000					$ 0	$ 13,318,000	$ 42,089,000	[4]	$ 60,808,000	[4]	$ 0	$ 41,656,000	$ 13,436,000	$ 15,675,000	$ 30,000,000	$ 0	$ 38,255,000	$ 9,500,000
Less current maturities	(26,040,000)	(36,079,000)
Long-term debt - non-current	211,590,000	286,014,000
Interest rate swap , fixed interest rate (in hundredths)													4.41%	5.17%															3.46%	2.69%	2.45%					1.80%														2.065%
Effective, swaption interest rate (in hundredths)																			6.16%		4.67%								4.71%	3.94%	3.70%					4.47%														3.715%
Number of interest rate swap agreements held																									3
Aggregate net book value of secured assets	353,770,000
Aggregate principal payments for the next five years [Abstract]
2013	26,040,000
2014	26,227,000
2015	43,832,000
2016	36,503,000
2017	25,613,000
Thereafter	79,415,000
Maximum borrowing capacity				30,000,000	35,000,000		42,000,000					30,000,000						23,300,000
Line of credit facility, extended expiration date			Apr. 30, 2013				Apr. 30, 2014
Letter of credit cancelled			6,400,000
Proceeds from borrowings of line of credit			9,500,000						45,900,000						24,200,000	12,700,000	6,100,000
Commitment fee on undrawn portion of facility (in hundredths)			0.125%
Repayments of long term lines of credit						12,000,000
Loans pledged as collateral						$ 3,745,000
Long-term debt weighted average interest rate (in hundredths)	3.2645%	3.4593%
Term of financing agreement								7 years			7 years	5 years
Number of tranches								2
Number of previously leased vessels										2

[1] We have interest rate swap agreements in place to fix the interest rates on our variable rate notes payable expiring in 2012 and 2015 at 5.17% and 4.41%, respectively. After applicable margin adjustments, the effective interest rates on these notes payable are fixed at 4.67% and 6.16%, respectively. The swap agreements are for the same terms as the associated notes payable. The variable rate note expiring in 2012 along with the associated swap was repaid at termination.

[2] We had three interest rate swap agreements currently in place to fix the interest rate on portions of this variable note payable at 3.46%, 2.69% and 2.45% respectively through the termination of the loan. After applicable margin adjustments, the effective interest rates on the swapped portion of these notes payable are 4.71%, 3.94% and 3.70%, respectively. Two of these swap agreements became effective in 2010 when the previous swap agreements terminated and the remaining agreement has been in place since the inception of the loan. This loan was prepaid during 2012 and the associated swaps were terminated at that time.

[3] We had an interest rate swap agreement in place to fix the interest rate on our variable rate note payable expiring in 2018 at 1.80%. After applicable margin adjustments, the effective interest rate on this note payable is fixed at 4.47%. The swap agreement is for the same term as the associated note payable. This loan was prepaid during 2012 and the associated swap was terminated at that time.

[4] We have an interest rate swap agreement in place to fix the interest rate on our variable rate note payable expiring in 2020 at 2.065%. After applicable margin adjustments, the effective interest rate on this note payable is fixed at 3.715%. The swap agreement is for the same term as the associated note payable.