Goodwill and Other Intangible Assets (Other Intangibles-Aquired) (Details) (WPD Midlands [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
Apr. 30, 2011 Integer	Dec. 31, 2011
Easements [Member]
Acquired indefinite-lived intangible assets: [Line Items]
Gross carrying amount		$ 88
Contracts [Member]
Acquired finite-lived intangible assets: [Line Items]
Amount resulting from acquistion		$ 10
Weighted-average amortization period (in years)	10

The aggregate amount assigned to a major class of finite-lived intangible assets acquired either individually or as part of a group of assets (in either an asset acquisition or business combination). A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16265-109275

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 44

-Subparagraph a(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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