|**Investments in Equity Securities**                   | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
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|**Investments, Debt and Equity Securities [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Investments in Equity Securities                       | Investments in Equity SecuritiesInvestments in equity securities, the majority of which are carried at fair value, are summarized as follows:March 31,December 31,20202019amounts in thousandsCharter (a)$2,337,9242,599,253Other investments (b)5,2856,040$2,343,2092,605,293(a) A portion of the Charter equity securities are considered covered shares and subject to certain contractual restrictions in accordance with the indemnification agreement. See note 3 for additional discussion of the indemnification agreement.(b) The Company has elected the measurement alternative for a portion of these securities where the fair value is not readily determinable.
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|Charter (a)                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Other investments (b)                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
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