Retirement Plans (Cash Contributions For Qualified Pension Plan Benefit Payments For Non-Qualified OPEB Plans) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash contribution to non-qualified OPEB plan	$ 22	$ 24
Pension Non-qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash contributions to non-qualified pension plan	$ 30	$ 29

Amount of cash outflow for other postretirement benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes pension benefit.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585

Name:	us-gaap_OtherPostretirementBenefitsPayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration