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Business (Narrative) (Details) - USD ($)
$ in Millions
Jul. 28, 2020
Jun. 30, 2020
Dec. 31, 2019
Business Acquisition [Line Items]      
Cash and short-term investments   $ 71.4 $ 87.8
Subsequent Event [Member] | Tetraphase Pharmaceuticals, Inc. [Member]      
Business Acquisition [Line Items]      
Upfront cash for acquisition $ 43.0    
Future cash payments 16.0    
Additional aggregate payments $ 16.0