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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized and unrealized gains (losses) on financial instruments, net (note 2)	$ 1,417,560	$ 170,617	$ 1,484,968	$ 2,019,222
Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized and unrealized gains (losses) on financial instruments, net (note 2)	612,465	90,770	746,406	683,808
Investment In Liberty Broadband
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized and unrealized gains (losses) on financial instruments, net (note 2)	807,114	19,207	730,713	1,393,135
Derivative Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized and unrealized gains (losses) on financial instruments, net (note 2)	$ (2,019)	$ 60,640	$ 7,849	$ (57,721)