Notes Receivable (Narrative) (Details) (EnerBank [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delinquent loans	$ 5	$ 5
Loans modified as troubled debt restructurings	$ 1	$ 1

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

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