Note 3 - Revenue (Details Textual) $ in Thousands		12 Months Ended
	Dec. 30, 2019	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Revenue from Contract with Customer, Including Assessed Tax		$ 18,394	$ 43,997	$ 0
Clinical Trial Service Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax		394	25,975	0
Manufacturing Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax		$ 18,000	18,000	$ 0
Janssen [Member] | Clinical Trial Service Revenue [Member]
Transition Services Agreement, Number of Ongoing Clinical Trials Entered Into	2
Transition Services Agreement, Markup Percentage	30.00%
Proceeds from Customers			26,000
Janssen [Member] | Manufacturing Revenue [Member]
Proceeds from Customers			$ 18,000