Note 2 - Summary of Significant Accounting Policies - Anti-dilutive Securities (Details) - shares		6 Months Ended	12 Months Ended
		Dec. 31, 2017	Dec. 31, 2018	Jun. 30, 2017
Anti-dilutive securities (in shares)		5,985,166	68,694,403	5,285,805
Convertible Debt Securities [Member]
Anti-dilutive securities (in shares)			48,405,556
Vested Series A Warrants [Member]
Anti-dilutive securities (in shares)		404,412	404,412	404,412
Unvested Series A Warrants [Member]
Anti-dilutive securities (in shares)	[1]	698,529	698,529	698,529
Warrant, Other [Member]
Anti-dilutive securities (in shares)		3,725,782	16,162,267	3,725,782
Employee Stock Option [Member]
Anti-dilutive securities (in shares)		1,156,027	3,023,639	397,388
Restricted Stock Units (RSUs) [Member]
Anti-dilutive securities (in shares)		416		59,694

[1] The unvested Series A warrants were subject to vesting based upon the amount of funds actually received by the Company in the second close of the August 2015 financing which never occurred. The warrants will remain outstanding but unvested until they expire in February 2021.