Note 3 - Revenue From Contracts With Customers - Disaggregation of Revenue (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from contract with customer	$ 5,000	$ 22,000	$ 35,000	$ 303,000
Royalty [Member]
Revenue from contract with customer	4,895	2,382	13,985	9,842
Royalty [Member] \| Diagnostics Segment [Member]
Revenue from contract with customer	4,895	2,382	13,985	9,842
NAV4694 Sublicense [Member] \| Diagnostics Segment [Member]
Revenue from contract with customer		14,930		272,639
License [Member]
Revenue from contract with customer		19,930	9,953	277,639
License [Member] \| Diagnostics Segment [Member]
Revenue from contract with customer		19,930	9,953	277,639
Product and Service, Other [Member] \| Diagnostics Segment [Member]
Revenue from contract with customer			11,024	15,037
Europe [Member] \| Royalty [Member] \| Diagnostics Segment [Member]
Revenue from contract with customer	$ 4,895	2,382	$ 13,985	9,842
CHINA \| Expanded Tc99m Tilmanocept License Agreement [Member] \| Diagnostics Segment [Member]
Revenue from contract with customer		$ 5,000		$ 5,000