Note 9 - Subsequent Event (Details Textual) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2019	Nov. 05, 2019
Revenue from Contract with Customer, Including Assessed Tax		$ 19,059	$ 4,823
Torii Pharmaceutical Co. [Member]
Potential Milestone Payments Receivable if Regulatory Approval Before December 31, 2021					$ 15,000
Revenue from Contract with Customer, Including Assessed Tax			$ 1,053	$ 20,101
Torii Pharmaceutical Co. [Member] | Minimum [Member]
Royalty Rate if Maintains Sakigake Designation					20.00%
Torii Pharmaceutical Co. [Member] | Maximum [Member]
Royalty Rate if Maintains Sakigake Designation					40.00%
Torii Pharmaceutical Co. [Member] | Forecast [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 15,000