Consolidated Balance Sheets (Parentheticals) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, reserve	$ 2,472,345	$ 2,073,616
Accumulated depreciation, vessels	153,029,544	124,907,998
Accumulated amortization, other fixed assets	$ 832,541	$ 547,452
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	25,000,000	25,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	700,000,000	700,000,000
Common stock, issued (in shares)	71,502,206	71,055,400
Common stock, outstanding (in shares)	71,502,206	71,055,400