Revenue from Contracts with Customers (Narrative) (Details 1) - Gilead Sciences Incorporation [Member] $ in Millions	Sep. 30, 2021 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expect to recognize deferred research and development revenue	$ 7.1
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expect to recognize deferred research and development revenue	$ 16.4
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year