Assets and Liabilities Measured at Fair Value (Schedule of Realized and Unrealized Gains (Losses)) (Details) - USD ($) $ in Thousands  | 
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018  | 
Sep. 30, 2017  | 
Sep. 30, 2018  | 
Sep. 30, 2017  | 
|
| Fair Value Disclosures [Abstract] | ||||
| Equity securities | $ 175,359 | $ 143,158 | $ (53,681) | $ 405,655 | 
| Investment in Liberty Broadband | 366,211 | 364,930 | (36,706) | 906,136 | 
| Variable forward | (3,223) | (35,325) | 69,329 | (41,027) | 
| Indemnification obligation | (14,937) | 0 | 48,671 | 0 | 
| Exchangeable senior debentures | (27,901) | 0 | (31,941) | 0 | 
| Realized and unrealized gains (losses) on financial instruments, net | $ 495,509 | $ 472,763 | $ (4,328) | $ 1,270,764 | 
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- Definition Change In Fair Value Of Contingencies No definition available. 
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- Definition Change In Fair Value Of Long-Term Debt No definition available. 
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- Definition Gain (Loss) On Financial Instruments No definition available. 
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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- References No definition available. 
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- Definition Amount of realized and unrealized gain (loss) on investment. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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