Commitments And Contingencies (Environmental Remediation Contingencies) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Long-term Purchase Commitment [Line Items]
Amount of environmental loss accrual expected to be recovered	$ 678
Topock Site [Member]
Long-term Purchase Commitment [Line Items]
Remediation cost recovery	90.00%
Pacific Gas And Electric Company [Member]
Long-term Purchase Commitment [Line Items]
Increase in undiscounted future costs in the event other potentially responsible parties are not able to contribute	$ 1,800

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 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

Reference 2: 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=6393211&loc=d3e13022-110858

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