Retirement Plans (Amounts Included In Accumulated Other Comprehensive Income Expected To Be Amortized Into Net Periodic Cost (Benefit)) (Details) - Total 2015 Forecast [Member] $ in Millions	Dec. 31, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Prior service credit - AOCI	$ 14
Net actuarial loss - AOCI	(108)
Total amounts included in accumulated other comprehensive income expected to be amortized into net periodic cost (benefit)	(94)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service credit - AOCI
Net actuarial loss - AOCI	(99)
Total amounts included in accumulated other comprehensive income expected to be amortized into net periodic cost (benefit)	(99)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service credit - AOCI	14
Net actuarial loss - AOCI	(9)
Total amounts included in accumulated other comprehensive income expected to be amortized into net periodic cost (benefit)	$ 5