Note 10 - Stockholders' Equity - Warrant Activity (Details) - $ / shares	6 Months Ended	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Outstanding (in shares)	4,828,723	4,828,723	252,620
Outstanding, weighted average exercise price (in dollars per share)	$ 9.37	$ 9.37	$ 44.18
Warrants granted (in shares)			5,238,971
Warrants granted, weighted average exercise price (in dollars per share)			$ 9.83
Warrants exercised (cashless) (in shares)			(51,712)
Warrants exercised (cashless), weighted average exercise price (in dollars per share)			$ 13.60
Warrants expired/canceled (in shares)			(611,156)
Warrants expired/canceled, weighted average exercise price (in dollars per share)			$ 17.21
Outstanding (in shares)	4,828,723	4,828,723	4,828,723
Outstanding, weighted average exercise price (in dollars per share)	$ 9.37	$ 9.37	$ 9.37
Exercisable (in shares)	4,130,194	4,130,194	600,782
Exercisable, weighted average exercise price (in dollars per share)	$ 9.60	$ 9.60	$ 19.02