Accumulated Other Comprehensive Loss (Reconciliation Of The Components Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	$ 626	$ 200
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(60)	(273)
Investments, net pretax unrealized (losses) gains excluding non-credit component of other-than-temporary impairments	566	(73)
Deferred tax asset (liability)	(130)	15
Net unrealized (losses) gains on investments excluding non-credit component of other-than-temporary impairments	436	(58)
Non-credit component of other than temporary impairments on investments, unrealized losses	(4)	0
Non-credit component of other than temporary impairments on investments, deferred tax asset	1	0
Net unrealized non-credit component of other than temporary impairments on investments	(3)	0
Cash flow hedges, gross unrealized losses	(308)	(318)
Cash flow hedges, deferred tax asset	65	67
Net unrealized losses on cash flow hedges	(243)	(251)
Defined benefit pension plans, deferred net actuarial loss	(738)	(600)
Defined benefit pension plans, deferred prior service credits	(1)	(1)
Defined benefit pension plans, deferred tax asset	190	156
Net unrecognized periodic benefit costs for defined benefit pension plans	(549)	(445)
Postretirement benefit plans, deferred net actuarial loss	(57)	(76)
Postretirement beneft plans, prior service costs	28	40
Postretirement benefit plans, deferred tax asset	7	9
Net unrecognized periodic benefit costs for postretirement benefit plans	(22)	(27)
Foreign currency translation adjustments, gross unrealized losses	(3)	(2)
Foreign currency translation adjustments, deferred tax asset	1	0
Net unrealized losses on foreign currency translation adjustments	(2)	(2)
Accumulated other comprehensive loss	$ (383)	$ (783)	$ (986)