Acquisitions and Exit Activities (Restructuring and Related Costs) (Details) - Facility Closing $ in Millions	12 Months Ended
Dec. 31, 2015 USD ($)
Restructuring Cost and Reserve [Line Items]
Total Exit Activity Charges	$ 111
Fuel, purchased power, and gas — non-utility
Restructuring Cost and Reserve [Line Items]
Total Exit Activity Charges	5
Operation and maintenance
Restructuring Cost and Reserve [Line Items]
Total Exit Activity Charges	10
Asset (gains) losses and impairments, net
Restructuring Cost and Reserve [Line Items]
Total Exit Activity Charges	$ 96

Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan and expenses resulting from the write-down of assets. Excludes expenses related to a business combination, a discontinued operation or an asset retirement obligation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration