Income Tax Income Tax (Net Operating Loss Carryforward) (Details) $ in Millions	Dec. 31, 2020 USD ($)
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 900
No Expiration And No Valuation Allowance [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	103
Full Valuation Allowance [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	131
No Expiration And Partial Valuation Allowance [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	646
Expiration Dates Between 2029 And 2035 With No Valuation Allowance [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 20