Pension And Other Postretirement Benefits (Fair Value Of Benefit Plan Assets - Other Postretirement) (Details) - Other Postretirement Benefit Plans Defined Benefit [Member] - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, net asset value	[1]	$ 133	$ 109
Fair value of plan assets		425	386
U.S. Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, net asset value	[1]	81	64
Fair value of plan assets		81	64
Non-U.S. Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, net asset value	[1]	49	41
Fair value of plan assets		49	41
Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		92	88
Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		200	189
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, net asset value	[1]	3	4
Fair value of plan assets		3	4
Fair Value Inputs Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, fair value hierarchy		292	277
Fair Value Inputs Level 2 [Member] | Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, fair value hierarchy	[2]	92	88
Fair Value Inputs Level 2 [Member] | Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, fair value hierarchy	[2]	$ 200	$ 189

[1] Per ASU 2015-07, certain instruments that are measured at fair value using the Net Asset Value (NAV) per share practical expedient have not been categorized in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the total value of plan assets.

[2] For corporate, government and asset-backed debt securities, fair value is based on observable inputs of comparable market transactions.