Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Accounts receivable, reserve	$ 1,837	$ 1,818
Vessels and vessel improvements, accumulated depreciation	230,318	218,670
Other fixed assets, accumulated depreciation	$ 1,452	$ 1,403
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	700,000,000	700,000,000
Common stock, shares issued (in shares)	12,985,994	12,917,027
Common stock outstanding (in shares)	12,985,994	12,917,027