Summarized Financial Information of Unconsolidated Affiliate Summarized Balance Sheet of Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Financial Support for Nonconsolidated Legal Entity [Line Items]
Current Assets of Unconsolidated Affiliates	$ 18	$ 21
Non-current Assets of Unconsolidated Affiliates	15	18
Current Liabilities of Unconsolidated Affiliates	9	13
Non-current Liabilities of Unconsolidated Affiliates	$ 11	$ 10