Long-Term Debt (Details) (USD $)	3 Months Ended			3 Months Ended		1 Months Ended	3 Months Ended				1 Months Ended						3 Months Ended				3 Months Ended				3 Months Ended		3 Months Ended				3 Months Ended	12 Months Ended	3 Months Ended				3 Months Ended				3 Months Ended		3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Jun. 20, 2011 Tranche	Mar. 31, 2013 Revolving Credit Facility [Member]	Nov. 28, 2012 Revolving Credit Facility [Member]	Jan. 31, 2013 Revolving Credit Facility One [Member]	Mar. 31, 2013 Revolving Credit Facility One [Member]	Jun. 20, 2011 ING Bank [Member]	Nov. 30, 2012 Capital One N.A [Member]	Mar. 31, 2013 Notes Payable - Variable Rate 2015 [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]	Mar. 31, 2013 Secured Debt [Member] Notes Payable - Variable Rate 2015 [Member]	Mar. 31, 2013 Secured Debt [Member] Notes Payable - Variable Rate 2020 [Member]	Mar. 31, 2013 Unsecured Line of Credit [Member]		Dec. 31, 2012 Unsecured Line of Credit [Member]		Mar. 31, 2013 G. Ridge [Member] Secured Debt [Member] Notes Payable - Variable Rate 2015 [Member]		Dec. 31, 2012 G. Ridge [Member] Secured Debt [Member] Notes Payable - Variable Rate 2015 [Member]		Mar. 31, 2013 O. Wave [Member] Secured Debt [Member] Notes Payable - Variable Rate 2017b [Member]	Dec. 31, 2012 O. Wave [Member] Secured Debt [Member] Notes Payable - Variable Rate 2017b [Member]	Mar. 31, 2013 UOS [Member] Secured Debt [Member] Notes Payable Variable Rate 2017c [Member]		Dec. 31, 2012 UOS [Member] Secured Debt [Member] Notes Payable Variable Rate 2017c [Member]		Mar. 31, 2013 Crest/Tide [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member]	Dec. 31, 2012 Crest/Tide [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018d [Member]	Mar. 31, 2013 Australia [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche A [Member]		Dec. 31, 2012 Australia [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche A [Member]		Mar. 31, 2013 Americas [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche B [Member]		Dec. 31, 2012 Americas [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018, Tranche B [Member]		Mar. 31, 2013 G. Dale [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018c [Member]	Dec. 31, 2012 G. Dale [Member] Secured Debt [Member] Notes Payable - Variable Rate 2018c [Member]	Mar. 31, 2013 Rio Geike [Member] Secured Debt [Member] Notes Payable - Variable Rate 2020 [Member]		Dec. 31, 2012 Rio Geike [Member] Secured Debt [Member] Notes Payable - Variable Rate 2020 [Member]
Long-term Debt [Abstract]
Interest rate (in hundredths)																	3.96%	[1]	3.9597%	[1]	2.0346%	[2]	2.06%	[2]	2.5537%	2.559%	2.7037%	[3]	2.709%	[3]			2.7801%	[4]	2.809%	[4]	2.8158%	[4]	2.8158%	[4]	2.9536%	2.981%	1.81%	[5]	1.8314%	[5]
Interest rate, minimum (in hundredths)																															2.78%	2.81%
Interest rate, maximum (in hundredths)																															2.80%	2.85%
Maturity date																	2014	[1]			2015	[2]			2017		2017	[3]			2018		2018	[4]			2018	[4]			2018		2020	[5]
Total principal due	$ 216,044,000	$ 237,630,000															$ 26,255,000	[1]	$ 38,255,000	[1]	$ 12,000,000	[2]	$ 12,666,000	[2]	$ 13,063,000	$ 13,436,000	$ 28,500,000	[3]	$ 30,000,000	[3]	$ 47,840,000	$ 48,760,000	$ 18,038,000	[4]	$ 18,896,000	[4]	$ 17,593,000	[4]	$ 17,908,000	[4]	$ 14,910,000	$ 15,620,000	$ 37,845,000	[5]	$ 42,089,000	[5]
Less current maturities	(25,729,000)	(26,040,000)
Long-term debt - non-current	190,315,000	211,590,000
Interest rate swap , fixed interest rate (in hundredths)										4.41%						2.065%
Effective, swaption interest rate (in hundredths)															6.16%	3.715%
Term of financing agreement								7 years	5 years
Maximum borrowing capacity					30,000,000		42,000,000		30,000,000					23,300,000
Business acquisition interest in acquiree (in hundredths)	100.00%
Number of tranches			2
Proceeds from borrowings of line of credit											24,200,000	12,700,000	6,100,000
Repayments of long term lines of credit						12,000,000
Line of credit facility, extended expiration date				Jan. 31, 2013			Jul. 31, 2014
Loans pledged as collateral						3,745,000
Long-term debt weighted average interest rate (in hundredths)	3.3469%	3.2645%
Line of credit facility, fully drawn	$ 9,000,000

[1] Effective November 28, 2012, our revolving credit facility was increased from $30 million to $42 million to provide additional funds for working capital purposes. This revolver was considered fully drawn at December 31, 2012 and the $12 million increase was fully repaid in January 2013. At the point of repayment, the revolving credit facility was reduced back to $30 million with $3.745 million used as collateral for various letters of credit. At March 31, 2013, the $30 million revolver was considered fully drawn with $9 million repaid in early April 2013. The expiration of this facility is July of 2014. The net weighted average interest rate on all of our long-term debt after consideration of the effect of our interest rate swaps at March 31, 2013 and December 31, 2012 was 3.3469% and 3.2645%, respectively.

[2] We have interest rate swap agreements in place to fix the interest rate on our variable rate note payable expiring in 2015 at 4.41%. After applicable margin adjustments, the effective interest rate on this note payable is fixed at 6.16%. The swap agreements are for the same terms as the associated note payable.

[3] We entered into a variable rate financing agreement with Capital One N.A. on November 30, 2012 for a five year facility totaling $30 million to finance a portion of the acquisition of UOS. This facility was fully drawn prior to the end of 2012.

[4] We entered into a variable rate financing agreement with ING Bank N.V., London branch on June 20, 2011 for a seven year facility to finance the acquisition of a Cape Size vessel and a Handymax Bulk Carrier Newbuilding, both of which we acquired a 100% interest in as a result of our acquisition of Dry Bulk. Pursuant to the terms of the facility, the lender agreed to provide a secured term loan facility divided into two tranches: Tranche A, fully drawn on June 20, 2011 in the amount of $24.2 million, and Tranche B, providing up to $23.3 million of additional credit. Under Tranche B, we drew $6.1 million in November 2011 and $12.7 million on January 24, 2012.

[5] 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.