Basis of Presentation (Narrative) (Details) $ in Millions		3 Months Ended
	Mar. 09, 2018	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Liberty Media | Affiliated Entity
Class of Stock [Line Items]
Reimbursable expenses		$ 2.3	$ 1.7
Liberty Ventures | Series A common stock
Class of Stock [Line Items]
Shares redemption ratio	1
Liberty Ventures | Series B common stock
Class of Stock [Line Items]
Shares redemption ratio	1