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Revenue Recognition Accounting Policy (Details 3) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]          
Total Revenues $ 1,339 $ 1,391 $ 3,903 $ 4,130  
Deferred Revenue $ 418   418   $ 414
Deferred Revenue, Revenue Recognized     (47)    
Deferred Revenue, Additions     $ 51