Investments in Equity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments in equity securities	$ 1,673,580	$ 1,803,064
1.75% Exchangeable Debentures | Indemnification obligation | LI LLC | GCI Liberty
Schedule of Trading Securities and Other Trading Assets [Line Items]
Interest rate	1.75%
Charter
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments in equity securities	$ 1,667,642	1,800,208
Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments in equity securities	$ 5,938	$ 2,856