Income Taxes Income Taxes - Operating Loss and Tax Credit Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 531	$ 637
Tax Credit Carryforwards	230	205
Total Operating Loss and Tax Credit Carryforwards	761	842
Expiring within Five Years [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	131	78
Tax Credit Carryforwards	30	27
Expiring After Five Years Or Having Indefinite Expiration [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	400	559
Tax Credit Carryforwards	$ 200	$ 178