Commitments, Guarantees and Contingencies - Solid and Hazardous Waste (Details) (Manufactured Gas Plant Site [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Manufactured Gas Plant Site [Member]
Solid and Hazardous Waste [Line Items]
Remediation Costs Liability	$ 0.5

Carrying amount of the liability for remediation of environmental damage pertaining to assets or businesses previously disposed.

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 4

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q4)

-URI http://asc.fasb.org/extlink&oid=6572457&loc=d3e149879-122751

Name:	us-gaap_EnvironmentalExitCostsAssetsPreviouslyDisposedLiabilityForRemediation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant