Quarterly report pursuant to Section 13 or 15(d)

Investments in Equity Securities (Details)

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Investments in Equity Securities (Details) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]    
Investments in equity securities $ 2,343,209 $ 2,605,293
Other investments    
Debt and Equity Securities, FV-NI [Line Items]    
Investments in equity securities 5,285 6,040
Charter    
Debt and Equity Securities, FV-NI [Line Items]    
Investments in equity securities $ 2,337,924 $ 2,599,253