Note 4 - Fair Value Measurements - Contingent Consideration Liabilities (Details) $ in Millions	Mar. 31, 2019 USD ($)
Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon First Commercial Sale [Member]
Contingent Consideration	$ 23
Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon Achievement of All Levels of Net Sales [Member]
Contingent Consideration	70
Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon Achievement of Net Sales Level 2 [Member]
Contingent Consideration	5
Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon Achievement of Net Sales Level 3 [Member]
Contingent Consideration	10
Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon Achievement of Net Sales Level 4 [Member]
Contingent Consideration	20
Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon Achievement of Net Sales Level 5 [Member]
Contingent Consideration	30
Milestone Payment upon Achievement of Net Sales Level 1 [Member] | Milestone Payment upon Achievement of All Levels of Net Sales [Member]
Contingent Consideration	5
AZEDRA Program [Member] | Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon First Commercial Sale [Member]
Contingent Consideration	8
The 1404 Program [Member] | Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon First Commercial Sale [Member]
Contingent Consideration	10
The 1095 Program[Member] | Molecular Insight Pharmaceuticals, Inc. [Member] | Milestone Payment upon First Commercial Sale [Member]
Contingent Consideration	$ 5