Investments in Affiliates Accounted for Using the Equity Method (Investment in Liberty Broadband) (Details) $ / shares in Units, $ in Thousands	May 18, 2016 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2015 $ / shares
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method		$ 174,134	$ 114,655
Series A common stock | Charter
Schedule of Equity Method Investments [Line Items]
Shares, exchange ratio	1
Liberty Broadband
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method		$ 3,598,079	3,634,786
Percentage ownership		23.50%
Liberty Broadband | Series C Non-voting Shares
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method	$ 2,400,000
Liberty Broadband | Series C Common Stock
Schedule of Equity Method Investments [Line Items]
Per share price of stock purchased (in dollars per share) | $ / shares				$ 56.23
Charter | Liberty Broadband
Schedule of Equity Method Investments [Line Items]
Investments accounted for using the equity method		$ 11,977,368	$ 11,835,613
Payments to acquire investments	$ 5,000,000