Basis of Presentation (Narrative) (Details) - Affiliated Entity - GCI Liberty $ in Millions		3 Months Ended
	Mar. 09, 2018	Mar. 31, 2018 USD ($)
Liberty Ventures | Class A Common Stock
Class of Stock [Line Items]
Shares redemption ratio	1
Liberty Ventures | Class B Common Stock
Class of Stock [Line Items]
Shares redemption ratio	1
Liberty Media
Class of Stock [Line Items]
Reimbursable expenses		$ 1.7