Note 9 - Stockholders' Equity - Unvested Units Expected to Vest (Details) - shares	Dec. 31, 2016	Dec. 31, 2015
Units scheduled to vest (in shares)	2,735,564	3,375,798
Share-based Compensation Award, Tranche One [Member]
Units scheduled to vest (in shares)	790,253
Share-based Compensation Award, Tranche Two [Member]
Units scheduled to vest (in shares)	650,137
Share-based Compensation Award, Tranche Three [Member]
Units scheduled to vest (in shares)	379,743
Share-based Compensation Award, Tranche Four [Member]
Units scheduled to vest (in shares)	579,437
Share-based Compensation Award, Tranche Five [Member]
Units scheduled to vest (in shares)	335,994