Changes In Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 25	$ (315)	$ 25	$ (315)	$ (250)	$ (139)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			273	(177)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(2)	(1)
Other comprehensive income (loss)	148	(49)	275	(176)
Other Comprehensive Income (Loss), Tax			90	(58)
Other Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	9	(289)	9	(289)	228	(114)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			237	(175)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0	0
Other comprehensive income (loss)			237	(175)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax			78	(58)
Other Pension, Postretirement and Supplemental Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	37	(3)	37	(3)	(1)	(2)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			36	(2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(2)	(1)
Other comprehensive income (loss)			38	(1)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax			12	0
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (21)	$ (23)	(21)	(23)	$ (21)	$ (23)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0	0
Other comprehensive income (loss)			0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax			$ 0	$ 0