QUARTERLY FINANCIAL INFORMATION - (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Information [Abstract]
Revenues	$ 56,810	$ 61,162	$ 60,320	$ 65,204	$ 61,814	$ 67,087	$ 69,961	$ 64,334	$ 243,496	$ 263,196	$ 290,049
Voyage Expenses	45,262	45,394	47,026	50,826	44,367	46,911	51,814	48,990	188,508	192,082	209,347
Operating Income	10,128	4,013	3,518	6,312	5,395	8,632	6,727	22,855	23,971	43,609	16,183
Net Income	$ 11,540	$ 1,782	$ 704	$ 7,936	$ 1,781	$ 2,850	$ 2,838	$ 24,080	$ 21,962	$ 31,549	$ 15,302
Basic and Diluted Earnings per Common Share [Abstract]
Basic Earnings Per Common Share (in dollars per share)	$ 1.60	$ 0.25	$ 0.10	$ 1.11	$ 0.25	$ 0.40	$ 0.39	$ 3.33	$ 3.05	$ 4.42	$ 2.14
Diluted Earnings Per Common Share (in dollars per share)	$ 1.60	$ 0.25	$ 0.10	$ 1.11	$ 0.25	$ 0.40	$ 0.39	$ 3.32	$ 3.04	$ 4.40	$ 2.12