Annual report pursuant to Section 13 and 15(d)

Business & Basis of Presentation (Details)

v3.10.0.1
Business & Basis of Presentation (Details)
$ / shares in Units, $ in Billions
 6 Months Ended 12 Months Ended
Mar. 31, 2019
USD ($)
shares
Dec. 31, 2018
segment
satellite_radio_system
$ / shares
Sep. 23, 2018
$ / shares
Dec. 31, 2017
$ / shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]        
Number of satellite radio systems | satellite_radio_system   2    
Business Combinations [Abstract]        
Common stock, par value (in dollars per share)   $ 0.001 $ 0.001 $ 0.001
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]        
Number of reportable segments | segment   1    
Common Stock | Management | Liberty Media        
Related Party Transactions [Abstract]        
Related party ownership percentage   73.00%    
Pandora        
Business Combinations [Abstract]        
Common stock, par value (in dollars per share)     $ 0.0001  
Pandora | Forecast        
Business Combinations [Abstract]        
Agreement value | $ $ 3.5      
Shares issuable per acquiree share (in shares) | shares 1.44      
Minimum        
Related Party Transaction [Line Items]        
Length of prepaid subscriptions, term   3 months    
Maximum        
Related Party Transaction [Line Items]        
Length of prepaid subscriptions, term   12 months