Note 3 - Revenue - Potential Milestone Payments Received (Details) - Collaborative Arrangement [Member] $ in Millions	Mar. 31, 2023 USD ($)
Research And Development Milestone Payments [Member]
milestone	$ 1,997
Research And Development Milestone Payments [Member] | Astra Zeneca A B [Member]
milestone	504
Research And Development Milestone Payments [Member] | Les Laboratoires Servier And Institut De Recherches Internationales Servier [Member]
milestone	20
Research And Development Milestone Payments [Member] | Seattle Genetics Inc. [Member]
milestone	759
Research And Development Milestone Payments [Member] | Boston Pharmaceuticals [Member]
milestone	88
Research And Development Milestone Payments [Member] | Genentech [Member]
milestone	626
Sales Milestone Payments [Member]
milestone	4,915
Sales Milestone Payments [Member] | Astra Zeneca A B [Member]
milestone	3,750
Sales Milestone Payments [Member] | Les Laboratoires Servier And Institut De Recherches Internationales Servier [Member]
milestone	0
Sales Milestone Payments [Member] | Seattle Genetics Inc. [Member]
milestone	450
Sales Milestone Payments [Member] | Boston Pharmaceuticals [Member]
milestone	265
Sales Milestone Payments [Member] | Genentech [Member]
milestone	$ 450