Note 15 - Selected Quarterly Financial Data (Unaudited) - Schedule of Quarterly Infomation (Details) - USD ($)	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total revenues	$ 24,019,051		$ 14,404,979		$ 11,073,502		$ 11,538,272		$ 3,750,538		$ 1,465,121						$ 61,035,804	$ 5,215,659
Operating loss	(2,657,037)		(6,342,528)		(3,709,594)		(3,183,707)		(1,609,725)		(1,483,406)		(603,330)		(3,833,323)		(15,892,866)	(7,529,784)	(2,333,091)
Net loss	$ (2,599,892)		$ (6,235,543)		$ (3,487,971)		$ (3,093,143)		$ (1,535,087)		$ (1,532,698)		$ (612,799)		$ (3,834,565)		$ (15,416,549)	$ (7,515,149)	$ (2,335,013)
Basic (in dollars per share)	$ (0.07)	[1]	$ (0.16)	[1]	$ (0.09)	[1]	$ (0.10)	[1]		[2]		[2]		[2]		[2]
Diluted (in dollars per share)	$ (0.07)	[1]	$ (0.16)	[1]	$ (0.09)	[1]	$ (0.10)	[1]		[2]		[2]		[2]		[2]

[1] The sum of quarterly per share amounts may not equal amounts reported for year-to-date periods due to the effects of rounding.

[2] For all quarters in 2016, this presentation is not applicable as the Company was not a public company until February 8, 2017.