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Property, Equipment and Intangible Assets (Narrative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Equipment and Intangible Assets [Abstract]            
Depreciation and amortization       $ 25 $ 25 $ 22
Amortization of Intangible Assets $ 3 $ 10 $ 16