Income Taxes (Tax Carryforwards) (Details) $ in Millions	Dec. 31, 2020 USD ($)
Tax Credit Carryforward [Line Items]
Tax Credit Carryforwards	$ 959
Tax Loss Carryforwards	1,164
Expiration Period Current To Five Years [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforwards	50
Tax Loss Carryforwards	126
Expiration Period Six To Ten Years [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforwards	38
Tax Loss Carryforwards	58
Expiration Period Eleven To Twenty Years [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforwards	341
Tax Loss Carryforwards	179
Expiration Period Indefinite [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforwards	530
Tax Loss Carryforwards	$ 801