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Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Service revenues	$ 8,604
Equity Method Investee [Member]
Related Party Transaction [Line Items]
Product costs	236	$ 226	$ 180
Accounts payable	18	20
Common Management Transaction [Member]
Related Party Transaction [Line Items]
Service revenues			144
Management Service [Member] \| Equity Method Investee [Member]
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 75	$ 67	$ 66