Income Taxes (Summary of Operating Losses and Tax Credits) (Details) $ in Millions	Dec. 31, 2016 USD ($)
United States
Operating Loss Carryforwards [Line Items]
Net operating loss	$ 54
Tax credits	52
State
Operating Loss Carryforwards [Line Items]
Net operating loss	175
Tax credits	1
Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss	$ 1,270