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Segment, Other Supplemental Information and Concentrations - Schedule of Revenue by Geographical Area (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Revenue $ 626 $ 526 $ 513 $ 491 $ 626 $ 552 $ 599 $ 545 $ 2,156 $ 2,322 $ 2,530
United States                      
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Revenue                 1,089 1,246 1,428
Americas (excluding United States)                      
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Revenue                 107 123 125
International                      
Revenues from External Customers and Long-Lived Assets [Line Items]                      
Revenue                 $ 960 $ 953 $ 977