Condensed Consolidated Balance Sheets (Parentheticals) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accumulated depreciation, vessels	$ 105,608,055	$ 99,910,416
Other fixed assets, accumulated amortization	$ 387,759	$ 343,799
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, issued (in shares)	70,515,018	70,394,307
Common stock, outstanding (in shares)	70,515,018	70,394,307