Annual report pursuant to Section 13 and 15(d)

Short-term Investments: Investment in Viking - Narrative (Details)

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Short-term Investments: Investment in Viking - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Aug. 31, 2014
Variable Interest Entity [Line Items]      
Investment in Viking common stock $ 32.8 $ 48.4  
Warrants $ 1.5    
Exercise price of warrants (USD per share) $ 1.50   $ 125.08
Equity Method Investee      
Variable Interest Entity [Line Items]      
Exercise price of warrants (USD per share) $ 1.50    
Warrants      
Variable Interest Entity [Line Items]      
Warrants investments in Viking $ 6.3 $ 9.9  
Viking Therapeutics, Inc.      
Variable Interest Entity [Line Items]      
Ownership interest (as a percent) 9.80%