Income Taxes (Summary of Operating Losses and Tax Credits) (Details) $ in Millions	Dec. 31, 2018 USD ($)
United States
Operating Loss Carryforwards [Line Items]
Net operating loss	$ 12
State
Operating Loss Carryforwards [Line Items]
Net operating loss	98
Tax credits	2
Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss	1,119
Tax credits	3
Excess Interest Expense | State
Operating Loss Carryforwards [Line Items]
Tax credits	$ 12