Retirement Plans (Schedule Of Pre-Tax Amounts Recognized In Accumulated Other Comprehensive Income/(Loss)) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost)/credit	$ 95
Net actuarial loss	(1,605)	(1,570)
Total pre-tax amounts recognized in accumulated other comprehensive income/(loss)	(1,510)	(1,570)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost)/credit
Net actuarial loss	(1,501)	(1,480)
Total pre-tax amounts recognized in accumulated other comprehensive income/(loss)	(1,501)	(1,480)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost)/credit	95
Net actuarial loss	(104)	(90)
Total pre-tax amounts recognized in accumulated other comprehensive income/(loss)	$ (9)	$ (90)