Commitments and Contingencies (Details) - Manufactured Gas Plant Sites - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Regulatory Assets	$ 670.7	$ 45.9
Reserves for Future Remediation	$ 608.6	$ 32.6

Amount of loss contingency liability.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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