Commitments And Contingencies (Environmental Remediation Contingencies) (Details) $ in Millions	Sep. 30, 2017 USD ($)
Long-term Purchase Commitment [Line Items]
Amount of environmental loss accrual expected to be recovered	$ 698
Increase in undiscounted future costs in the event other potentially responsible parties are not able to contribute	$ 1,000

Carrying amount as of the balance sheet date of known and reasonably estimable amounts of recoveries from third-parties pertaining to an entity's environmental remediation obligations. An entity's balance sheet may include several assets that relate to an environmental remediation obligation. Among them are the following: a. Receivables from other potentially responsible parties that are not providing initial funding; b. anticipated recoveries from insurers; and c. anticipated recoveries from prior owners as a result of indemnification agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64822958&loc=d3e13022-110858

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

Name:	us-gaap_RecordedThirdPartyEnvironmentalRecoveriesReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant