Quarterly report pursuant to Section 13 or 15(d)

Assets and Liabilities Measured at Fair Value - (Schedule of Assets and Liabilities) (Details)

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Assets and Liabilities Measured at Fair Value - (Schedule of Assets and Liabilities) (Details) - USD ($)
$ in Thousands
Sep. 30, 2020
Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash equivalents $ 438,545 $ 533,484
Equity securities 3,345,464 2,600,008
Investment in Liberty Broadband 6,097,955 5,367,242
Derivative instrument liability 63,456 71,305
Indemnification obligation 309,541 202,086
Exchangeable senior debentures    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Exchangeable senior debentures 820,035 658,839
Quoted prices in active markets for identical assets (Level 1)    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash equivalents 438,545 533,484
Equity securities 3,345,464 2,600,008
Investment in Liberty Broadband 6,097,955 5,367,242
Significant other observable inputs (Level 2)    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Derivative instrument liability 63,456 71,305
Indemnification obligation 309,541 202,086
Significant other observable inputs (Level 2) | Exchangeable senior debentures    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Exchangeable senior debentures $ 820,035 $ 658,839