Employee Benefit Plans (Amounts Included in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost in Subsequent Year) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	$ (4)
Amortization of actuarial (gain) loss, net	262
Total	258
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	6
Amortization of actuarial (gain) loss, net	17
Total	$ 23