Consolidated Balance Sheets (Parentheticals) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, reserve	$ 2,073,616	$ 3,501,964
Accumulated depreciation, vessels	124,907,998	99,910,416
Accumulated amortization, other fixed assets	$ 547,452	$ 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)	71,055,400	70,394,307
Common stock, outstanding (in shares)	71,055,400	70,394,307