Changes In Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 49	$ (361)	$ 49	$ (361)	$ (250)	$ (139)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			296	(224)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(3)	(2)
Other comprehensive income (loss)	23	(45)	299	(222)
Other Comprehensive Income (Loss), Tax			98	(73)
Other Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	29	(335)	29	(335)	228	(114)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			257	(221)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0	0
Other comprehensive income (loss)			257	(221)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax			84	(73)
Other Pension, Postretirement and Supplemental Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	41	(3)	41	(3)	(1)	(2)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			39	(3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(3)	(2)
Other comprehensive income (loss)			42	(1)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax			14	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