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Summary of Significant Accounting Policies - Principles of Consolidation and Research and Development (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Research and Development              
Research and development costs $ 5 $ 6 $ 11 $ 11 $ 21 $ 24 $ 33
Minimum              
Property and Equipment              
Useful life of property and equipment         2 years    
Maximum              
Property and Equipment              
Useful life of property and equipment         40 years    
Revenue Recognition              
Period of deferral for the portion of subscriber fees that are deferred     1 year   1 year