Note 8 - Stockholder's Equity - Stock Option Activity (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Options Exercised (in shares)	(700,165)	(4,693,918)
2012 Omnibus Incentive Plan [Member]
Outstanding at December 31, 2016 (in shares)	2,822,855
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 2.42
Options Granted (in shares)	257,500
Granted, Weighted- Average Exercise Price (in dollars per share)	$ 4.85
Options Exercised (in shares)	(14,165)
Exercised, Weighted- Average Exercise Price (in dollars per share)	$ 2.24
Options Forfeited or expired (in shares)	(1,667)
Forfeited or expired, Weighted- Average Exercise Price (in dollars per share)	$ 1.33
Outstanding at March 31, 2017 (in shares)	3,064,523	2,822,855
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 2.62	$ 2.42
Outstanding, Weighted Average Remaining Contractual Life (Year)	8 years 36 days
Outstanding, Aggregate Intrinsic Value	$ 10,008,824
Exercisable at March 31, 2017 (in shares)	1,443,130
Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 2.19
Exercisable, Weighted Average Remaining Contractual Life (Year)	7 years 109 days
Exercisable, Aggregate Intrinsic Value	$ 5,337,537
2006 Stock Incentive Plan [Member]
Outstanding at December 31, 2016 (in shares)	3,014,686
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 2.62
Options Granted (in shares)
Options Exercised (in shares)	(686,000)
Exercised, Weighted- Average Exercise Price (in dollars per share)	$ 1.07
Options Forfeited or expired (in shares)	(3,500)
Forfeited or expired, Weighted- Average Exercise Price (in dollars per share)	$ 4.36
Outstanding at March 31, 2017 (in shares)	2,352,186	3,014,686
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 3.06	$ 2.62
Outstanding, Weighted Average Remaining Contractual Life (Year)	3 years 109 days
Outstanding, Aggregate Intrinsic Value	$ 6,721,508
Exercisable at March 31, 2017 (in shares)	2,308,007
Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 3.05
Exercisable, Weighted Average Remaining Contractual Life (Year)	3 years 109 days
Exercisable, Aggregate Intrinsic Value	$ 6,624,756
The 2016 Inducement Omnibus Incentive Plan [Member]
Outstanding at December 31, 2016 (in shares)	310,000
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 6.02
Options Granted (in shares)	500,000
Granted, Weighted- Average Exercise Price (in dollars per share)	$ 4.83
Options Exercised (in shares)
Exercised, Weighted- Average Exercise Price (in dollars per share)
Options Forfeited or expired (in shares)	(35,000)
Forfeited or expired, Weighted- Average Exercise Price (in dollars per share)	$ 5.77
Outstanding at March 31, 2017 (in shares)	775,000	310,000
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 5.26	$ 6.02
Outstanding, Weighted Average Remaining Contractual Life (Year)	9 years 292 days
Outstanding, Aggregate Intrinsic Value	$ 544,925
Exercisable at March 31, 2017 (in shares)
Exercisable, Weighted- Average Exercise Price (in dollars per share)
Non-Plan Option Activity [Member]
Outstanding at December 31, 2016 (in shares)	316,456
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 1.34
Options Granted (in shares)
Granted, Weighted- Average Exercise Price (in dollars per share)
Options Exercised (in shares)
Exercised, Weighted- Average Exercise Price (in dollars per share)
Options Forfeited or expired (in shares)
Forfeited or expired, Weighted- Average Exercise Price (in dollars per share)
Outstanding at March 31, 2017 (in shares)	316,456	316,456
Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 1.34	$ 1.34
Outstanding, Weighted Average Remaining Contractual Life (Year)	2 years 219 days
Outstanding, Aggregate Intrinsic Value	$ 1,439,875
Exercisable at March 31, 2017 (in shares)	316,456
Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 1.34
Exercisable, Weighted Average Remaining Contractual Life (Year)	2 years 219 days
Exercisable, Aggregate Intrinsic Value	$ 1,439,875