Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Outstanding Awards) (Details)

v3.10.0.1
Stock-Based Compensation (Outstanding Awards) (Details)
shares in Millions, $ in Millions
12 Months Ended
Mar. 09, 2018
Dec. 31, 2018
USD ($)
shares
Series A common stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares reserved for issuance upon exercise | shares   1.7
Series B common stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares reserved for issuance upon exercise | shares   1.2
Options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Unrecognized compensation cost related to unvested options | $   $ 9.4
Weighted average period for compensation cost to be recognized   1 year 2 months 12 days
RSAs    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Unrecognized compensation cost related to unvested restricted shares | $   $ 24.2
Weighted average period for compensation cost to be recognized   1 year 11 months 19 days
Liberty Ventures | Series A common stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares redemption ratio 1  
Liberty Ventures | Series B common stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares redemption ratio 1