Unaudited Condensed Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Allowance for doubtful accounts of trade accounts receivable (in Dollars)	$ 304	$ 3,250
Accumulated depreciation for vessels and equipment (in Dollars)	401,830	389,469
Accumulated amortization of intangibles (in Dollars)	$ 15,137	$ 12,975
Preferred stock, shares authorized	2,000	2,000
Preferred stock, shares issued	0	0
Preferred stock, par value (in Dollars per share)	$ 0	$ 0
Common Class A [Member]
Common Stock, par value (in Dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	60,000	60,000
Common Stock, shares issued	26,811	26,941
Common Stock, shares outstanding	27,164	26,906
Common Class B [Member]
Common Stock, par value (in Dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	60,000	60,000
Common Stock, shares issued	0	0